Author Topic: Building a Modern Pneumatic Airgun  (Read 122866 times)

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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Offline Stot

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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
Science is fun.

We're all mad here. I'm mad. You're mad.

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
Stot
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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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Offline 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.

Offline Nitphoscine

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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?