Author Topic: Building a Modern Pneumatic Airgun  (Read 131334 times)

Offline Stot

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Building a Modern Pneumatic Airgun
« on: November 03, 2010, 08:28:15 AM »
Take 2....

Welllll....  Ive made lots since last time I posted, mostly gun stuff for my Air Rifles, but my current project is worthy of a project log.

I bought a book by H.M. Buckley called The Modern Pneumatic Airgun.   Its a well written explanation on the theories behind operation, some nice machining tricks and full plans to design and build a PCP Air Rifle.  You can get the book by emailing Howard directly.   He also does a follow up book that concentrates on making an air rifle with the air tube in the stock rather than under the barrel, like a Gunpower rifle.

I'm at the stage where I have accumulates most of the materials to make the rifles and spent maybe 60 to get enough material for 2 full rifles + some spare parts.  The most expensive part is the barrel as this cant really be made at home.  Its not impossible, but impractical.  Luckilly I managed to pick up a 24" .22 barrel for just 20.



Ill keep a log of what Im doing here..  Hopefully. :poke:
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Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #1 on: November 03, 2010, 08:38:46 AM »
Ok part 2...

First thing to do was prepare the air tubes.   You can make these any length you want within reason, but the longer they are, the more air stored, the more shots you get.   With the UK limit of 12ft.lbf for an unlicenced airgun, these air tubes at 450mm long should get 70 shots or so in .22.  

I used aluminium for the air tube hence the thick wall.  These will be holding 3000psi+

So basically the pics below show that I.
  • chucked up the tube
  • faced off the end
  • Measured the bore with some telescoping guages and a micrometer
  • bored out the tube slightly to the minor size for the thread I was cutting
  • cut the thread.









I use an old 2 flute milling bit as a boring tool.  They work really well for this.





Repeat 3 more times and give a cursory polish.  :thumbup:



Cheers
Stot
« Last Edit: November 03, 2010, 08:43:14 AM by Stot »
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Offline Brass_Machine

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Re: Building a Modern Pneumatic Airgun
« Reply #2 on: November 03, 2010, 10:42:13 AM »
Thanks Stot for reposting. Got a lot of guys interested in this one :)

Eric
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Offline j45on

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Re: Building a Modern Pneumatic Airgun
« Reply #3 on: November 03, 2010, 02:33:56 PM »
Interesting stuff  :thumbup: keep it coming

Edit : will you be making a pump as well or do you decant from another bottle ?
And how much is the book ?
« Last Edit: November 03, 2010, 04:47:06 PM by j45on »
Jason

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #4 on: November 03, 2010, 04:59:30 PM »
Hi Jason,

I have an FX pump that will pump up to 250bar.   I don't have a bottle, I'm too lazy to keep getting them filled.  :coffee:

The book was 30 + post,   13 air mail or 8 surface mail USA / rest of the world; 6.50 Europe and 4.50 UK.  Its a big old book.

Cheers
Stot
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Offline Stot

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Update 2 - Inlet Valve Housing
« Reply #5 on: November 04, 2010, 06:27:40 PM »
Ok 1/2 way though the air inlet valve.

The ends of the air tube are brass valves.  One end allows air in only at the muzzle end, the other end is a poppet hammer valve that will momentarily open to allow air to escape.

As far as machining goes the brass valve housings are 80% the same, so ill cover it once here, and then just show what Is different on the poppet valve when I do that.

The Inlet end calls for a standard 1/8 BSF high pressure air thread for filling.  This is where I am making my first change to the design.  I wont be using the standard fitting to fill, instead I will use a BSA style quick fill probe.  This works by just slipping an o-ringed probe into a filler port and starting to fill. ( more on that when i do the other end )

So,  Starting with a piece of solid brass I...

  • Faced off the bar and drilled and bored a series of 3 stepped holes.  These will house a sprung valve pin that acts as a 1 way valve.  The pin and spring is held in by a plug screw and the largest hole will be threaded later.
  • Turned the outside to be the major diameter of the thread to match the air tube.
  • Turned a step in the end of the valve housing to allow an o-ring to be positioned inside the unthreaded section of the airtube.
  • Threaded the valve housing to match the air tube.
  • Threaded the inside of the valve housing to take the plug screw.



























Thats as far as I got tonight.  Still, making good progress so far. :D

Cheers
Stot
« Last Edit: November 28, 2010, 09:50:10 AM by Stot »
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Offline Brass_Machine

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Re: Building a Modern Pneumatic Airgun
« Reply #6 on: November 04, 2010, 07:45:50 PM »
-- fixed your image tags. Fro some reason the pictures weren't showing up.

Very nice work. Threading looks great!

Eric
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Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #7 on: November 05, 2010, 03:26:51 AM »
-- fixed your image tags. Fro some reason the pictures weren't showing up.

Very nice work. Threading looks great!

Eric

Cheers Eric,  I must have left the ?attredirects=0 bit on the images.  :doh:

I put the good threads down to having a nice big sturdy machine.  :thumbup:

Cheers
Stot
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Offline Gerhard Olivier

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Re: Building a Modern Pneumatic Airgun
« Reply #8 on: November 05, 2010, 05:15:40 AM »
Nice job Stot

Keep it coming - hungry for more.

Gerhard
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Offline Brass_Machine

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Re: Building a Modern Pneumatic Airgun
« Reply #9 on: November 05, 2010, 10:38:12 AM »
Cheers Eric,  I must have left the ?attredirects=0 bit on the images.  :doh:

I put the good threads down to having a nice big sturdy machine.  :thumbup:

Cheers
Stot

Yup. No big deal. :)

Eric
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Offline Stot

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Update 3 - Inlet Valve Housing
« Reply #10 on: November 06, 2010, 10:26:34 AM »
Found a few hours this morning to finish the other end of my inlet valve, and make the other one too.  :clap:

The fill end of the valve would normally be just a threaded nub to connect to an air hose, kinda like a tyre valve.   I decided to go with a quick fill valve instead.   With the quick fill valve you have a probe on your air line with a hole coing through it crossways instead of out the end and 2 o-rings either side of the probes outlet.

You push the probe into a hole cross drilled into the end of the valve and as you pump the pressure seals the probe in by pushing in opposite directions against the two o-rings.  When you're done filling you relieve the pressure and just pull out the probe.  You can see the probe in the last couple of pics.

So, this part I...
  • Used the air tube as a mandrel for the valve.  This made it easier to hold and not damage the threads.
  • Turned down the end to have 3 steps, and faced it off down to dimension/
  • I files the burs off the edges and that was the turning done.
  • Mounted the valve in my 4 jaw chuck so that I could cross drill it.
  • I used an end mill smaller than the hole I wanted to make just to make sure I had the valve centered.  Its easy to see if a cylinder is centered by the mark an end mill makes.
  • Center drilled and then drilled a small hole all the way through the valve.
  • Drilled a hole the size of the fill probe to a preset depth.  I put an o-ring on the drill bit to let me know how far to drill.  This hole doesnt go all the way through but stops a couple of mm in from the other side.
  • Used a center drill to chamfer the edges so it doesn't damage the o-rings on the probe.































Thats the inlet valve housings done for both rifles.  The valve internals ill do in the week.

Cheers
Stot
« Last Edit: November 28, 2010, 09:49:24 AM by Stot »
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Offline Powder Keg

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Re: Building a Modern Pneumatic Airgun
« Reply #11 on: November 06, 2010, 11:22:12 AM »
Looking great so far!! I am interested in Air guns. But have never had the time to build one or even mod the ones that I own. I have the plans for 2 or three including one that looks like a cane. I would like to build that one one day:o)

Keep up the good work!!!
Wesley P
A Gismo ??? If it has a flywheel or spins and is made with small parts. I'll take one! If it makes noise, moves, or requires frequent oiling and dusting it's a better deal yet. It's especially right if its shiny and bright; but if it's dirty and dull it wont mater at all...

Offline johnbaz

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Re: Building a Modern Pneumatic Airgun
« Reply #12 on: November 06, 2010, 11:45:14 AM »
COR!! - This is sooo intersting!!, i love airguns and can't wait for the next update :clap:

My precharged rifles, the career has given me a hell of a lot of trouble but i have it shooting smoothly now, also the Huntsman sporter developed a leak, i had to strip it and re-face the valve as it had a nick in the face...



Good luck with the build :thumbup:


John :dremel:

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #13 on: November 06, 2010, 12:10:11 PM »
Nice collection.  I have a 2 PCPs, a Parker Hale Phoenix and a BSA Ultra Multishot.  I also Have a Theoben SLR98, BSA Meteor, ASI Paratrooper, HW45 Pistol, Gamo P800 Pistol and a S&W 686 Pistol.

I did have an Alros Trailsman too and its a real simple take down PCP rifle.  Really easy to make so I think ill make my own version of that some day too.

I'd like to see that cane gun too.  Youre not allowed them here in the UK I believe Its classed as a concealed weapon.  ::)

I have other plans I bough for a multi stroke pneumatic rifle that look good too.

Cheers
Stot
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Offline johnbaz

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Re: Building a Modern Pneumatic Airgun
« Reply #14 on: November 06, 2010, 12:47:27 PM »
Hi Stot

I thought you were allowed to have the walking stick (air)guns as long as you didn't have any rounds for them, i think they all use obsolete calibres  ::)

I turned one down about fifteen years ago, it needed repairs but was only 30 :(

Here's the rest of my collection..


I also have a pistol collection, Webley's and BSA 240's



John :beer:

Offline Stot

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Update 4 - Poppet Valve Housing
« Reply #15 on: November 07, 2010, 09:31:40 AM »
Did the outlet valve housings today.

The outlet valves are poppet valves.  A sprung hammer strikes them to open the valve and let some air out, simple stuff really.

They are pretty much the same as the inlet valves other than the hole goes straight through which will hold the valve pin of the poppet valve, and the end is threaded to go into the hammer housing that will be made later.  There are still holes to be cross drilled on these but their position is dependant on the breech and trigger blocks so ill drill them when those parts are done.

As this is the pretty much the same operations as Ive already done,  Just some finished item shots. ;)











Cheers
Stot
« Last Edit: November 28, 2010, 09:48:40 AM by Stot »
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Offline Powder Keg

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Re: Building a Modern Pneumatic Airgun
« Reply #16 on: November 07, 2010, 10:36:28 AM »
Very professional looking parts there. I'm watching this one closely(o:
Wesley P
A Gismo ??? If it has a flywheel or spins and is made with small parts. I'll take one! If it makes noise, moves, or requires frequent oiling and dusting it's a better deal yet. It's especially right if its shiny and bright; but if it's dirty and dull it wont mater at all...

Offline j45on

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Re: Building a Modern Pneumatic Airgun
« Reply #17 on: November 07, 2010, 10:44:59 AM »
Me to  :bow:
I was not aware you could build your own air gun until I saw this thread
as I said before interesting stuff
Jason

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #18 on: November 07, 2010, 11:06:23 AM »
Its bloody adictive too!   Im having to limit myself to 2-3 hours a day.  I've got about 10 hours in it so far and its mostly been by the book.

Ill do the valve internals tomorrow but I have to take a look at the hammer tube and bolt arangement now because I'm not overly keen on having a seperate bolt and hammer handles.

Cheers
Stot
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Offline johnbaz

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Re: Building a Modern Pneumatic Airgun
« Reply #19 on: November 07, 2010, 03:53:51 PM »
Fantastic work Stot- those threads are just soooooo smooooth :clap:

It's addictive reading too!!! :thumbup:


Cheers, John :beer:

Offline Brass_Machine

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Re: Building a Modern Pneumatic Airgun
« Reply #20 on: November 07, 2010, 04:23:02 PM »
OK, so I have to get that book so I can follow along with what you are doing.

I see another hobby on my horizon.

Eric
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Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #21 on: November 07, 2010, 04:49:52 PM »
OK, so I have to get that book so I can follow along with what you are doing.

I see another hobby on my horizon.

Eric

Ill be finished the gun by the time you get the book.  :lol:

If you do want it email Howard but hes old school so you wont get a reply for a while, But you will get a reply none the less.  :thumbup:

Cheers
Stot
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Offline Blade

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Re: Building a Modern Pneumatic Airgun
« Reply #22 on: November 07, 2010, 11:01:52 PM »
Great work! Can't wait to see how these finish out.

Offline Fred Bloggs

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Re: Building a Modern Pneumatic Airgun
« Reply #23 on: November 08, 2010, 11:14:01 AM »
Hi everyone

Saw the thread  :jaw:, thought great got to get me the book, so emailed Howard and he replied the same day, I think he's going to have quite alot of business in the next few weeks.

great work Stot

Fred

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #24 on: November 08, 2010, 05:24:42 PM »
Great stuff.  Hope he does sell a few its a great book and a bargain for the info contained.

What I will say is make sure you know the law regarding air rifles before you start.  Its easy to fall outside of the law without knowing it and you could get in real trouble.

Cheers
Stot
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Offline JimM

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Re: Building a Modern Pneumatic Airgun
« Reply #25 on: November 11, 2010, 03:40:41 PM »
Great work there Stot, if the rest turns out as well as the parts so far it's going to be a beauty. Will you be making the stock as well or just the mechanicals?

Cheers

Jim
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Location: Chessington, Surrey

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #26 on: November 12, 2010, 04:50:58 AM »
Great work there Stot, if the rest turns out as well as the parts so far it's going to be a beauty. Will you be making the stock as well or just the mechanicals?

Cheers

Jim
(a HW80K owner)

Not for these one.  I bought 2 stocks of ebay for 9 each posted so if they will work ill use those first.  :thumbup:

Cheers
Stot
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Offline Stot

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Update 5 - Valve Plugs
« Reply #27 on: November 12, 2010, 05:24:04 AM »
Right next up I made the plugs for the valves.  They are threaded brass plugs with a stub to locate the valve spring on, a slot to screw it in and holes for airways.

I started off trying to make them all as one piece then parting off but had a little mishap when I was chamfering the edges for threading and snapped off 3 of them so ended up making them as 2 pairs.
:doh:
There are some milling operations here to cut the slot and drill the holes but I came up with a way to do the lot on the lathe.   The holes were easy, use the 4 jaw chuck and mount the parts off center to drill the holes.   Other than in future using a center drill to start them this worked well.

The slot however slightly more difficult, you could mount an end mill or slitting saw in the lathe, then mount the part on the cross slide and cut the slot, but I have a Unimat SL, So I made a stand for it out of an old indicator stand and clamped it to my cross slide.   Lined up the slitting saw in it with the lathe center line and used the lathe feeds to cut my slot.  :borg:  I can use this as a toolpost grinder in future too.  :ddb:

So below pics showed that I..

  • Turned down the brass bar to major thread diameter and cut recesses with my parting tool.
  • Chamfered the edges for threading.
  • Broke it..  So chucked it up to do just 2 of them./
  • Threaded the bar.
  • Ground an edge on the bottom of an old hacksaw blade and parted off each one, wasting as little as possible.
  • Made the other two the same way.
  • Mounted each one in the lathe to face them off and clean them up.
  • Set up my Unimat SL head on the cross slide.
  • Used an end mill mounted in the chuck to set my slitting saw to center line.
  • Cut the slots.
  • Changed to the 4 jaw chuck and mounted the part off center for hole drilling.
  • Drilled the holes. (I'd use a center drill to start them next time as one slipped)

Other than cleaning up with a needle file thats it.   The last picture is the first attempt at these which I wasnt happy with.  The slitting saw arbour was slipping in the chuck so they all went off center.  Although they would be functional, they arent 'A Game' stuff, so rejected for these rifles.  :dremel:



































Cheers
Stot
« Last Edit: November 28, 2010, 09:47:56 AM by Stot »
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Offline Stot

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Update 6 - Inlet Valve Internals
« Reply #28 on: November 15, 2010, 06:45:01 AM »
Two updates today from the weekend.

First up I made the air inlet valve internals.  Very simple one way valves with an o-ring seal.  Only bit im not making is the O-Ring.  :borg:

So below I,
  • Chucked up some stock and turned it to fit inside the valve housing.
  • Turned a section to slip inside the through-hole in the valve housing.
  • Parted off and flipped it around in the chuck.
  • Turned the spring guide end. That part is done.
  • Mounted a suitable bar in the lathe to make the size of spring I wanted.  pinch the music wire in the chuck and start hand cranking the chuck.
  • After a couple of turns to get a spring started, engage the half-nut to set the carriage moving at the spring TPI youre after and turn for desired length of spring.  Disengage half-nut and finish the spring with a couple of turns.
  • Clean the springs up and all parts ready for assembley.

















Tested these and they hold 30bar pressure overnight so at the moment, jobs a goodun.   :beer:

Cheers
Stot
« Last Edit: November 28, 2010, 09:47:17 AM by Stot »
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Offline Stot

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Update 7 - Poppet Valve Internals
« Reply #29 on: November 15, 2010, 08:17:18 AM »
Ok so part 2-2, the Poppet valve internals.

I am veering slightly from the book valve design that uses a flat seated valve.  I am going to use a tapered valve seat and seal which I feel has better redundancy in the design, and has better air flow characteristics.

So,
  • Cut the valve seat into the valve body.
  • Chucked up some Delrin to make the valve seal.
  • Drilled a hole to thread onto the valve stem.
  • Parted off using a 60 degree tool bit.
  • 2 valve seals.
  • Chucked up some bar to cut the valve stem.  This is a bit big, but I had it around so it will do. :D
  • Turned it down to a 'go' fit to the valve housing then polished it up.
  • Turned down to make a thread for the seal to go on. Threaded.
  • Parted off and mounted in the chuck again.
  • Threaded the Delrin seal onto the rod.
  • Cleaned up the seal face and cut the spring guide onto the back of it.
  • Assembled the valve with a spring made the same as the one above.







































Filled to 70bar overnight just to see it held pressure.  No problems.   :headbang:

Cheers
Stot
« Last Edit: November 28, 2010, 09:46:26 AM by Stot »
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Offline Jonny

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Re: Building a Modern Pneumatic Airgun
« Reply #30 on: November 15, 2010, 11:36:14 AM »
Nice to see some one else in to it.
Havent made any for close on 8 years the laws have changed since. The last ones been on hold ever since but essentially made and lingering around some where.
I wouldnt pay any attention to those books, make it up as you go on and you will learn a lot more than any book to date has to offer.

Looking at it, yes it will work but know you will have trouble with that knock open valve. It drove me round the bend 19 years ago trying to self regulate them valves to acceptable limits. In the end made a regulator similar to the late Mick Dawes design often copied and used in other rifles, Anchutz, BSA, ISP and more.

Pressure tested the tube? 1 1/2 times the operating pressure, shame manufacturers dont do that. No reason to doubt your threads wont hold the pressure but its a safety thing!
Can do it with a modded grease gun and clock, fill air tube with water and pump oil in. 1/8"BSP off the shelf hydraulic will shear at 6300psi.

Why aint you making the stock, small bore tube easy and quick.

Heres an early one that packed up in 2005 used three times a week for 12 years.
http://pic20.picturetrail.com/VOL15/728921/1313294/111432614.jpg
Number 7 1996 rotting away http://pic20.picturetrail.com/VOL15/728921/1313294/15295231.jpg

Last one been on hold since Maarch 2004
http://pic20.picturetrail.com/VOL15/728921/1723145/20512931.jpg
http://pic20.picturetrail.com/VOL15/728921/1723145/20513282.jpg
http://pic20.picturetrail.com/VOL15/728921/1723145/21294937.jpg
http://pic20.picturetrail.com/VOL15/728921/1723145/303431797.jpg
Tube is done not shown, just needs O rings and a lot of faffing about to get it right, then theres the making of the stock, easy.

Theres over 6k's worth here. http://pic20.picturetrail.com/VOL15/728921/8449063/360648667.jpg
« Last Edit: November 15, 2010, 03:48:06 PM by Jonny »

Offline Jonny

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Re: Building a Modern Pneumatic Airgun
« Reply #31 on: November 15, 2010, 11:37:28 AM »
Actually you can up that a 1000+ theres a March scope on it at the moment.

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #32 on: November 15, 2010, 02:58:47 PM »
The test fill to 70bar was just to see if it would seal but yeah ill pressure test it up to 4-500 bar depending on if I regulate it.  I have regulated my BSA Ultra and love the consistency and it sure would make spring balancing easier...  :lol:

Nice stuff there right at the pioneering end of modern PCPs.  :smart: Impressive FT rig, not my cuppa though, I'm more into practical hunting stuff.  Love my Phoenix, it looks like a stalking rifle and does the job really well.   The stocks I got off Ebay are going to work really well I think, especially as these are just for my own use. They are comfortable for me and just need re-inletting but thats the easy bit.



Cheers
Stot
« Last Edit: November 15, 2010, 03:47:25 PM by Stot »
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Offline JimM

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Re: Building a Modern Pneumatic Airgun
« Reply #33 on: November 15, 2010, 03:40:01 PM »
Location: Chessington, Surrey

Offline Jonny

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Re: Building a Modern Pneumatic Airgun
« Reply #34 on: November 15, 2010, 03:47:16 PM »
Would be bordering semi bullpup with that stock, usually rear of action is level at the front of pistol grip.
My first ones the rear end hammer to valve was short, really short then set back a bit, thumbhole under trigger block.
Sussed out short stroking back in 92 without side effects- 1.4mm hammer stroke, presentable at 2.8mm. To date no one sussed even now only running 5.5mm.

The fill probe first used by Titan in 93 a reverseal of what i came up with on first two guns plus Stalker, now used on AA what did they ever design.

Any ideas for a trigger :bang:
Single stage real easy, two stage very very hard to get right.
Did a semi bullpup in 95 in stainless G316 S11, trigger block 13" long no linkages and long first stage returning. Could hold in vice blow on blade and it would go off.

Its what i was good at back then because i didnt read from a book and understood how things should work and be made, a book cant teach that.

Offline Jonny

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Re: Building a Modern Pneumatic Airgun
« Reply #35 on: November 15, 2010, 03:57:38 PM »
Yes typo that pound sign, duly altered.
Serious dosh not for use down the cut, scope was near 1200 6 years ago but can pay 3k now with mounts.

First air rifles made cost me around 20 for the wood, 20 butt pad, 6 hydraulic tube, 5 springs and screws, free barrel and approx 15 of ancilliary items.

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #36 on: November 15, 2010, 04:00:41 PM »
I have an idea for an adjustable 2 stage trigger but not sure on it at the moment I need to do some testing to see if it will work as I hope.

Your current gun reminds me of the Alros Trailsman TDR.  Trigger on that was very... agricultural and is what gave me the idea for the trigger i'm planning as I wanted to replace the trigger on it.

Quote
Did a semi bullpup in 95 in stainless G316 S11, trigger block 13" long no linkages and long first stage returning. Could hold in vice blow on blade and it would go off.

That sounds similar to what I have in mind only twice as long, but I'll leave the details until I'm there though, just incase It fails miserably and I change it completely. :D

Cheers
Stot
« Last Edit: November 15, 2010, 04:03:29 PM by Stot »
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Offline cfellows

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Re: Building a Modern Pneumatic Airgun
« Reply #37 on: November 19, 2010, 11:16:11 AM »
Just found this thread and have read through it with interest.  I have both of Buckley's books, but in the end, I built a bulk CO2 air rifle based more on the Stealth layout.  I like your poppet valve approach better than Buckley's.  What's the diameter of the delrin valve head?  Also, what size thread did you use on the valve stem?

Thx...
Chuck

Here's a link to my CO2 air rifle...

http://www.youtube.com/watch?v=1n-EXv5lLbE

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #38 on: November 19, 2010, 04:46:59 PM »
I like your poppet valve approach better than Buckley's.  What's the diameter of the delrin valve head?  Also, what size thread did you use on the valve stem?

Hi Chuck,

I seen your video before actually when I was first looking at building something its a great setup.  :clap:  Great thing about the book design is it should run nicely on CO2 with just a little adjustment, especially with a 24" barrel.  :thumbup:

The book doesn't cover the poppet valve head too well in the schematics.  Theres no sizes or anything for making the seal and cap.  Also looking at the recess in the pin that aids airflow in the schematics, it looks like its in the wrong place, i.e. the edge of the recess is in line with the transfer port with the pin is at rest, rather than when the valve is open.  So I decided to do it my way.

The poppet valve head is 9mm-6.5mm @ 60 degrees.  I threaded the valve pin M4 and left a shoulder on it then self tapped it into a 3mm hole in the delrin.   I had to re-design the valve pin to accommodate the tapered seat but it seals real nice.

Haven't done anything on it this week, Got to get the hammer tube done over the weekend and im coing to case harden the valve pins too.  :coffee:

Cheers
Stot

« Last Edit: November 19, 2010, 05:35:37 PM by Stot »
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Offline Stot

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Update 8 - Hammers
« Reply #39 on: November 22, 2010, 05:33:01 PM »
Well a few days since my last update but I'm at a stage where parts of the design for one part is dependant on the design and position of another part.

As standard the book rifle has seperate hammer cocking handle and bolt handle.  I want the rifles to be bolt cocking only so I have had to redesign the breech block, the bolt, the hammer and the hammer tube slightly.  Also roughed up the trigger assembley so now I have positions of all the areas I have to mill on the hammer tube and breech.

I threaded the hammer tube to take fit the valve the same way I did the air tubes and what this all means is the last parts I have to turn are the bolt and handle, the hammer and the hammer tube end cap.  The rest is milling operations so Ill get the turning out of the way then set the lathe
up for milling and do the lot.

First up was the hammers.

  • Threaded the hammer tubes to fit on the valves.
  • Faced off and turned down some stock to slip fit the hammer tube.
  • Center drilled then drilled through the stock.
  • Bored out a recess for the hammer spring to guide in.
  • Turned the stock around and turned the other end down under size.  This is because the shoulder that is left will be the sear.
  • Polished it up, hammer done.



























Ill case harden these too so the sears work nicely.   :thumbup:

Cheers
Stot
« Last Edit: November 28, 2010, 09:45:25 AM by Stot »
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Offline Dean W

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Re: Building a Modern Pneumatic Airgun
« Reply #40 on: November 22, 2010, 11:49:51 PM »
Great thread you have here, Stot.  I've thought about building an air rifle a few times, but it always gets
pushed aside for engine or shop projects.  Being a long time shooter, both air and firearms, this build has a
lot of interest for me.  Maybe I'll get to it someday.  Glad you are posting up your progress.

Dean
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Offline Stot

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Update 9 - Pellet Probe Bolts
« Reply #41 on: November 25, 2010, 03:13:54 AM »
Another update.  I made one of the bolts/pellet probe.   I wasnt sure wether to make this out of steel or brass.  Steel would be easier for me, I hate machining brass because I end up pulling splinters out of every appendage for days.  :bang:

I had a scrap of brass big enough, and I think it will accent well with the brass valves and trigger, so I bit the bullet and made it from that.  I did wear some nitrile gloves which helped a lot with the splinters.  :thumbup:

The pellet probes are calibre specific, my rifles will be .22 to start with although I may convert one to .177 later. I can turn a .22 probe down to .177, but not the other way so I'll make them both .22 for now.

Very simple turning operations to make the bolt, but it will be cross drilled for a pin to be screwed into when I'm set up for milling.  The bolt handle can be put on either side in my re-design for a fully ambedextrous(sp?) operation.

  • Chucked up the rough brass I had and turned it down to the same diameter as my barrels.  This means I just need to drill one size hole through the breech block.
  • Turned it around, parted it off and turned it down to just under the barrel bore size.
  • Turned down the tip of the probe that will push the pellet past the barrel transfer port.
  • Polished it up a bit.
  • Turned it around again and made a threadded hole for the bolt handle bolt.

























You can see where ive marked for an o-ring on the end of the probe to seal the barrel when cocked, but Im not sure what o-ring ill be using yet so ill cut the groove when I have the o-ring.

Cheers
Stot
« Last Edit: November 28, 2010, 09:44:55 AM by Stot »
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Offline Stot

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Update 10 - Case Hardening Hammers
« Reply #42 on: November 28, 2010, 09:42:27 AM »
This week I ar bin mostly turnin'.   Well that and a little case hardnening.

The ridge on the hammers makes up part of the sears in the trigger, so it makes sense to harden them so they don't wear easily.  The steel I had was EN1A So case hardening it is the only way to go.  Also the tip of the hammer is an adjustable screw and as this is what will take the brunt of the impact force so hardening the threads is sensible too.

I wasnt sure if I was going to get the hammers hot enough with just a propane/butane blow torch but it came up a very nice cherry red.  I cant file or scribe them when done so jobs a good un.  :dremel:  You dont get a real sense of the red of the metal in the photos because of the flash but here you go.

  • Heated up the hammer until cherry red.
  • Dip in hardening compound.
  • Keep red hot for 5 mins minimum.
  • Quench in water.

















Its easy to do really.  I turned them around and did the skirt end of the hammer too as the trigger sears will rub along them during the cocking stroke and i don't want them to wear.  The hammers will be polished back up before use.

Cheers
Stot
« Last Edit: November 28, 2010, 09:43:59 AM by Stot »
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Offline Stot

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Update 11 - Hammer Tube End Cap
« Reply #43 on: November 28, 2010, 09:59:40 AM »
The Turning I have done was the hammer tube end caps.  These dont screw in, they are held in place by a bolt from underneath that also holds the trigger block on.  Basic slip fit caps really.

This is the penultimate bit of turning, last thing is to drill through the breech block for the barrel and bolt and then ill set the lathe up for milling.  :zap:

  • Chucked some brass stock the same as the valves were made from.
  • Turn down to slip fit the hammer tube.
  • Chamfer the edges and polish up a bit with wet and dry and some scotch brite pad.
  • Part off.
  • Mount the part in the lathe and face off to size.
  • Chamfer the back of the cap to taste. Polish this end.





















And a couple of pictures of all the parts so far.  :)





Cheers
Stot
« Last Edit: November 28, 2010, 10:01:11 AM by Stot »
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Offline cfellows

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Re: Building a Modern Pneumatic Airgun
« Reply #44 on: November 28, 2010, 10:36:18 AM »
Nice progress, Stot.  I'm particularly impressed with your finish on everything.  By they way, what kind of gloves are you wearing, and why?  Just wondered if that's something I should consider?

Chuck

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Re: Building a Modern Pneumatic Airgun
« Reply #45 on: November 28, 2010, 12:32:16 PM »
Hi Chuck,

Thanks for the comments.  Im trying to get these as A grade as I can just to see if I can.   I still have an A game gun out of the pair and the B game gun is filled with the first attempt parts.  Still its going to be a good standard. ;)

The gloves are just nitrite workshop gloves.  I've started wearing them when im working with brass.  It stops me getting splinters in my hands and they wont tear my hand off if they get caught on the chuck like normal gloves could..

Cheers
Stot
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Re: Building a Modern Pneumatic Airgun
« Reply #46 on: November 28, 2010, 01:56:05 PM »
they wont tear my hand off if they get caught on the chuck



Are you sure?  My brother started wearing those when working. His usual MO when using a portable drill was to grip the revolving chuck to tighten and loosen the chuck. I do the same, but with bare hands. Luckily he broke only one of his fingers, as the extra grip provided by the glove rather took him by surprise. ::)

Pete

Offline j45on

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Re: Building a Modern Pneumatic Airgun
« Reply #47 on: November 28, 2010, 02:28:39 PM »
I use these as a mechanic and they will indeed fall apart very easily latex ones have more stretch and and will wrap around a drill or impact gun along with your hand
Jason

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #48 on: November 28, 2010, 02:34:13 PM »
Yeah Like Jason says, the Nitrile ones have far less stretch before they tear.   I have to change mine a couple of times a session from just changing tools.

Cheers
Stot
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Re: Building a Modern Pneumatic Airgun
« Reply #49 on: November 28, 2010, 06:48:32 PM »
Thanks both. Useful info to pass on.

Pete

Offline Jonny

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Re: Building a Modern Pneumatic Airgun
« Reply #50 on: November 28, 2010, 06:56:49 PM »
I only wear gloves in conditions outdoors like yesterday and today.

Brass does hurt when taking a cut coming off a wall 5 foot away but extremely rarely use it. Not even for the valves, well first three were manganese bronze similar. Either steel, stainless or aluminium, brass i have a phobia it just looks cheap.

Looks like similar arrangement to the Titan valving and in response earlier regarding size, its relevant to port through hole behind acetal valve. Same as Titan/Falcon smaller is better and still think you will have long term probs with cutting acetal valve at same angle as brass.
On a flat it will sound better, close easier and seal better after run in.
For this you will have to make several valves to see what size and shape is best.

Nothing like an Alros thats a proper two stage trigger using Vanadis and M5 tool steel for main two sears, ground wont last 5 mins.

Even copying others it still takes more time than its worth, to design and work everything out on first 3 i made if got 50p/hr would have had to charge around 10k ea including hand made stocks.
For the last 17 years more involved in the aftermarket accessories worldwide.




Offline Brass_Machine

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Re: Building a Modern Pneumatic Airgun
« Reply #51 on: November 28, 2010, 07:51:25 PM »
Nice work!

Hoegaarden glass for quenching... hehe. One of my favorite beers...

Eric
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Update 12 - Breech part 1
« Reply #52 on: December 01, 2010, 06:35:02 PM »
Got some work done on the breeches this week.

There are a few turning and milling operations so I did the turning and set the lathe up for milling the the rest of this and most of the other parts from now on.

Standard design for this part is for a single shot.  I've re-designed it a bit to allow use of a 10 shot Daystate magazine.  Ill be making a single shot sled too, so even if the multi shot doesnt work out its not real loss.

To cut the dovetails for the scope mounting I decided to use a straight mill end and cut a slope in the sides to create the dovetail rather than use a dovetail mill end.   This is cheaper if you dont have a dovetail cutter, and I think looks better than a flat topped design.

As Im using the lathe to do my milling, Im using the measure 100 times, cut once rule.  ::)

So,

  • Mark the bore center on the bar stock and mount in the 4 jaw chuck.  Use a center to check alignment.
  • Drill out to size.
  • Check slip fit with the bolt.
  • Flip the bar around, check center and drill again.
  • Mark up for mounting holes, loading/magazine slot and dovetail position.
  • Set the lathe up for milling.
  • Found zero and check alignment using wriggler.  I made sure the wriggler found zero at the same point both ends.
  • Drill center holes, then drill through holes.
  • Cut slot for magazine.
  • Set up tilting table at 30 degrees to cut a 60 degree dovetail.
  • Figure out how to mount the breech in the right postion without a proper hold down kit this size.  :bang:
  • Cut one side of dovetail. Flip over and cut the other side.
  • Finish the end of at an angle.























































Still more to do on these, but so far so good.

Cheers
Stot
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Offline Jonny

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Re: Building a Modern Pneumatic Airgun
« Reply #53 on: December 01, 2010, 07:32:28 PM »
You need a miller saves all the faffing about.
In saying that first 7 was done with just a Myford ML7, took an eternity.

Dovetail cutters are cheap i have loads even for 3/8 rails used on German.
Picatinny

German to suit Sportsmatch rail
Long breach block, short rear where yours is long, cant believe this is No7 in Tungum alloy tube December 1995, piccy about 8 years ago and rotting away. 5th side lever.


Front looks quite short but will be ok. Looks thin where machined out for mag ie flex. Decent barrel fit in to breach unlike what you are copying using grub screws to centre barrel.


Offline Brass_Machine

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Re: Update 12 - Breech part 1
« Reply #54 on: December 01, 2010, 10:23:39 PM »
...

As Im using the lathe to do my milling, Im using the measure 100 times, cut once rule.  ::)

...

And doing a great job of it. Those look stellar.

Eric
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Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #55 on: December 02, 2010, 02:12:07 AM »
You need a miller saves all the faffing about.
In saying that first 7 was done with just a Myford ML7, took an eternity.

Front looks quite short but will be ok. Looks thin where machined out for mag ie flex. Decent barrel fit in to breach unlike what you are copying using grub screws to centre barrel.

Some lovely work there Jonny.   I have a big old 7HP mill but its a 2 ton job that wont fit in the house I'm in at the moment.  Moving next year so hopefully Ill look for someplace with a big garage that will let me use it.  :thumbup:

I did have reservations about the barrel end of the breech but it will be supported up front with a barrel band, so it should be fine and will help minimise any flex imparted on the magazine slot.  If I went free floating I would have made it a lot longer and id be more concerned about he slot.  I've made it 5mm bigger than the design in the book anyway and added an extra grub screw. 

Also added the extra mounting holes.  In the book it only has 2 in the front and 2 at the back so I added another 2 at the back again to help minimise any flexing that may occur.

Cheers
Stot
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Offline Stot

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Re: Update 12 - Breech part 1
« Reply #56 on: December 02, 2010, 02:17:24 AM »
And doing a great job of it. Those look stellar.

Eric

Cheers Eric.  :beer:
Stot
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Offline cfellows

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Re: Building a Modern Pneumatic Airgun
« Reply #57 on: December 06, 2010, 12:49:11 AM »
Maybe I missed this somewhere in your thread... what are the ID and OD of the aluminum air tubes used for reservoirs?

Thx...
Chuck

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #58 on: December 06, 2010, 05:05:52 AM »
The tube I'm using is 1 1/4" x 3/16" tube.   Ill pressure test it before I use it properly but the way the o-rings work in the bore of the tube, it should be more than capable.

I've got the bits for pressure testing as Jonny described but I do need to make some adapters and stuff up.  I worked out that using water and oil to pressure test you only increase the volume by ~ 5% to reach 600bar pressure so any failures this way should just result in a crack and pop rather than a full on explosion. :bugeye:

Cheers
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Offline cfellows

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Re: Building a Modern Pneumatic Airgun
« Reply #59 on: December 06, 2010, 11:09:01 AM »
I was just curious.  I'm still noodling around with making a pump airgun.  Haven't decided whether to use steel or aluminum.  The pump and reservoir will all be part of the same tube.

Chuck

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #60 on: December 09, 2010, 04:30:10 AM »
I bought plans for a pump gun ages ago.  3 pumps 12ft.lbf But I'd love to try a single stroke up to that power.  I would go steel for a pump up as the thinner wall would allow for a larger swept volume in a less bulky rifle.

Cheers
Stot
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Update 13 - Breech Base
« Reply #61 on: December 10, 2010, 04:25:15 AM »
The breech needs to be dished out to sit on the hammer tube and valve properly.  With a mill and a ball nosed bit, easy but an 1 1/4" ball nosed mill end isnt cheap and I didnt have one.  :scratch:

An alternative is to set the mill up like a horizontal mill with a boring bar ( the type that takes HSS square tool steel ) in the chuck supported by a center at the other end and the bit set to 1 1/4" diameter, mount the breech on the toolpost and take passes.  I tried this on some scrap and it just didnt have the rigidity and chattered a lot no matter what I did.

Looking through my mill bits collection I found a normal 1 1/4" mill end so I ended up turning my angle plate through 90 degrees so that I could clamp the breech in the vise, bring it to center and take passes at the base to dish it out.   I could only get just over 1/2 way down the breech this way but thats fine because then I can flip it around and do the other side.  :ddb:

I also picked up this week an Ultrasonic cleaner from Maplins only 25 reduced from 45.  This is great for cleaning parts before assembley especially where you really dont want swarf clogging anything up.  It does wonders on brass.  :clap:

SO.  This time round I...

  • Milled trigger and bolt slots in the hammer tubes before I changed the lathe configuration.
  • Turned the angle plate 90 degrees and mounted the breech in the clamp.
  • Took passes at the base until I reached the desired depth.
  • Turned the breech around and milled in from the other side to the desired depth.
  • Used some spare tube and some wet'n'dry to finish the base to an exact fit to the tube.
  • Polished out most of the machine marks to a matt finish.
  • Cleaned in an ultrasonic cleaner.



























Cheers
Stot
« Last Edit: December 10, 2010, 10:44:48 AM by Stot »
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Offline cfellows

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Re: Building a Modern Pneumatic Airgun
« Reply #62 on: January 02, 2011, 04:28:40 PM »
Hey Stot,

Thought you might be interested in this video.  I'm firing .22 caliber pellets through my home made air gun and it is using High Pressure Air instead of CO2.  Noisy as the dickens and it sure does shoot hard!

http://www.youtube.com/watch?v=nYMU_6GhOCw

Chuck

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #63 on: January 06, 2011, 03:02:29 PM »
Nice Chuck.  Is the air regulated at 850psi?

I have a feeling these two guns will be quite a handful if allowed to go to full power so I'm trying really weak hammer springs to start off.  Havent really done much on them over the Christmas period but ill have an update soon.

Cheers
Stot
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Offline cfellows

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Re: Building a Modern Pneumatic Airgun
« Reply #64 on: January 12, 2011, 11:38:05 PM »
Nice Chuck.  Is the air regulated at 850psi?

I have a feeling these two guns will be quite a handful if allowed to go to full power so I'm trying really weak hammer springs to start off.  Havent really done much on them over the Christmas period but ill have an update soon.

Cheers
Stot

No, it's not regulated.  I've now got a slow leak around the release valve that I need to fix.

Chuck

Offline Jonny

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Re: Building a Modern Pneumatic Airgun
« Reply #65 on: January 13, 2011, 08:52:45 AM »
Coming on a bit now.
Did my first 7 breach blocks with made up long boring bar between centres with vertical slide, what a palava on a Myford took an eternity and still had to sand out the grooves.
Milled all the trigger blocks and sears that way.

Just doing that required a full rebuild every time, so careful with vertical slides.

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Re: Building a Modern Pneumatic Airgun
« Reply #66 on: February 22, 2011, 01:56:33 AM »
Ok part 2...

First thing to do was prepare the air tubes.   You can make these any length you want within reason, but the longer they are, the more air stored, the more shots you get.   With the UK limit of 12ft.lbf for an unlicenced airgun, these air tubes at 450mm long should get 70 shots or so in .22.  

I used aluminium for the air tube hence the thick wall.  These will be holding 3000psi+
What grade aluminium are you use for the air tube?
So basically the pics below show that I.
  • chucked up the tube
  • faced off the end
  • Measured the bore with some telescoping guages and a micrometer
  • bored out the tube slightly to the minor size for the thread I was cutting
  • cut the thread.









I use an old 2 flute milling bit as a boring tool.  They work really well for this.





Repeat 3 more times and give a cursory polish.  :thumbup:



Cheers
Stot

Offline Corvus corax

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Re: Building a Modern Pneumatic Airgun
« Reply #67 on: February 27, 2011, 08:45:44 AM »
I bought plans for a pump gun ages ago.  3 pumps 12ft.lbf But I'd love to try a single stroke up to that power.  I would go steel for a pump up as the thinner wall would allow for a larger swept volume in a less bulky rifle.

Cheers
Stot
Who offers plans for a pump rifle? All the commercial plans I find nowadays seem to be for PCP style rifles.

Offline j45on

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Re: Building a Modern Pneumatic Airgun
« Reply #68 on: February 28, 2011, 03:52:37 PM »
I bought plans for a pump gun ages ago.  3 pumps 12ft.lbf But I'd love to try a single stroke up to that power.  I would go steel for a pump up as the thinner wall would allow for a larger swept volume in a less bulky rifle.

Cheers
Stot
Who offers plans for a pump rifle? All the commercial plans I find nowadays seem to be for PCP style rifles.

Is this any good to you ?
http://www.john-tom.com/ForSale/ForSale.html#AirRiflePlans

This thread seems to have gone cold are you still out there Stot ?
« Last Edit: February 28, 2011, 03:56:07 PM by j45on »
Jason

Offline Corvus corax

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Re: Building a Modern Pneumatic Airgun
« Reply #69 on: March 03, 2011, 06:05:33 AM »
Thanks that's quite interesting. Anyone else seen these plans? Are they any good?

Offline keithomas

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Re: Building a Modern Pneumatic Airgun
« Reply #70 on: May 04, 2012, 02:15:39 PM »
is this project still rolling?