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Air Gun Home Forum Index » Rifles » my DIY .22 cal PCP airgun
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my DIY .22 cal PCP airgun 
PostPosted: Fri Nov 16, 2007 8:51 pm Reply with quote
dogon1013
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Joined: 15 Nov 2007
Posts: 58
Location: Sunshine State
I know I'm new here but I have been working on my own .22 caliber airgun for a few weeks and I thought I would get your opinoins about it. I downloaded the plans for the Caselman Air Machine gun after seeing the video. It's basically a PCP rifle and after seeing it saw thru a 2*4, I had to make my own, but I noticed that the design is very similar to several Paintball guns currently on the market, so I decided to try to convert a paintball gun to fire pellets.

I went with .22 caliber for the prototype since I could get a 20 inch .223 barrel blank for free. I have been shooting it single shot from a co2 tank for a while and it does work. I have made a magazine for it but I have not finished the attachment to the gun.

The gun is based on the action of the Kingman Spyder ACS E-marker. I replaced the bolt, made a chamber/magwell , barrel, and modified the valve. The magazine currently enters from the top, just like the paintball hopper but I hope to make it come from the side later. I have a small lathe at home and acces to a larger lathe, mill, lase, and welding equiptment at work.

I just got my 3000psi Air tank in and I will be "adjusting" the regulator to a higher pressure to get more velocity soon.


I have been shooting 22cal pellets (the traditionally shaped ones) as well as 40grain pulled .22lr bullets. I designed the magazine for these 40 grain bullets, as well as some 33 and 35 grain copper jacketed bullets I bought.

The 40 grain bullets penetrate about 1/4" (6.35mm) into a 2*4 using the ~700psi CO2. I don't have velicity numbers yet, but i will chrono it soon.

here are some pics:

I just added the gauge to the side.


here is the new air tank...it's big, but I got a good deal on it.


here it is with a 9 oz co2 tank.
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PostPosted: Fri Nov 16, 2007 9:15 pm Reply with quote
AirGunEric
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Interesting. Seeing as how it has a rifle barrel on it- why not add a forearm to make it easier to hold/control?

How well is it operating as a "machine gun"?

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PostPosted: Fri Nov 16, 2007 9:30 pm Reply with quote
dogon1013
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Joined: 15 Nov 2007
Posts: 58
Location: Sunshine State
A forearm and folding stock are on the list of things to buy or make, but first I want to get it working right. This is the first airgun I have made, so I'm sure there will be things to work out.

I have not finished the magazine latch that will hold the magazine in place so I have not been able to shoot it rapid fire yet. I've just loaded one in the top, and fired a few times.

it will dry-fire in full-auto nicelly...the electronic grip can go to 3-round burst, 6 round burst, or full auto. And the rate of fire can be adjusted from 6 Rounds per second, to 13 RPS.


I have the tank regulator apart right now and I need to shim the springs to get about 1500psi out of it..but its getting late so I will probably work on that tomorrow.
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PostPosted: Fri Nov 16, 2007 9:38 pm Reply with quote
AirGunEric
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Any pictures of the magazine setup and holder?

How are the pellets being loaded? In a regular paintball gun they just fall- being round and all this is easy- how did you get this to work with formed pellets/casings?

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PostPosted: Fri Nov 16, 2007 10:17 pm Reply with quote
dogon1013
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the mag is based off a traditional firearm box magazine. It's spring loaded and will not work with the traditional skirted pellets, only solid pellets can handle the spring pressure. the bolt feeds straight thrue the mags feed lips so the magazine can only be removed or inserted when the bolt is back. (the gun fires from an open bolt).

This feeding process will be the most difficult part of this airgun. reliable feeding will be necesary for rapid fire.

Ideally, I want to use these copper jacketed bullets:
http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=489745

Currently I do not have enough pressure to push these copper clad bullets thru the barrels rifling, but I can get lead bullets to shoot .That is why I have been using 40 grain bullets pulled form .22LR cartidges. the lead bullets also fit in the spring loaded magazine, but the lead might be too soft to feed reliably from the spring loaded mag. I may end up casting my own bullets for this airgun. I am eyeing this casting mold: http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=538620&t=11082005
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PostPosted: Sat Nov 17, 2007 12:13 am Reply with quote
Mar
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Crazyyyy!

You have too much time on your hands but that's quite the imagination, looks wicked. Twisted Evil
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PostPosted: Sat Nov 17, 2007 5:32 am Reply with quote
Alstone
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Welcome to the site there dogon1013, thats a fair piece of kit you have assembled, it could really qualify as a "Greaser". Smile

Nice work, makes life intresting seeing a bit of ingenuity.

Al


Last edited by Alstone on Sat Nov 17, 2007 7:03 pm; edited 2 times in total

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PostPosted: Sat Nov 17, 2007 6:15 pm Reply with quote
dogon1013
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Location: Sunshine State
here's some pictures of the magazine and some of the penetration tests. I was able to shim the springs in the regulator and get just over 1000psi out of it....looks like I'll need a bigger shim.

Here's the magazine lips with the 33grain copper bullets


Heres the mag with one of the 40gr lead bullets. the back of the mag is open so the bullet gets pushed straight thru the mag, by the bolt.


Here's the penetration tests, with the 1000psi shots circled. one of the shots is a 22 pellet, the other is a 40grain bullet. The other shots were done using 700psi.
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PostPosted: Sat Nov 17, 2007 10:08 pm Reply with quote
dogon1013
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Location: Sunshine State
well I got the magazine latch finished and It is feeding from the magazine, but the shot velocity is inconsistant and lower than it should be.

I think the extra friction from the magazine and mag spring is slowing the bolt/hammer down too much. Since this is basically an open bolt gun the chambering of a round, and the hammering of the valve pin are done from the same spring. I think I need to change this to a closed bolt system, so the friction from feeding the round from the mag and chambering it does not affect the hammer hitting the valve.

at least the dual chamber design of this paintball gun makes this closed bolt mod easy.
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PostPosted: Sat Nov 17, 2007 10:17 pm Reply with quote
AirGunEric
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It certainly seems to be an interesting project. I'd love to see a working loading system for it- that would be interesting for sure. Keep us up-to-date as things progress!

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PostPosted: Sun Nov 18, 2007 10:40 pm Reply with quote
dogon1013
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Joined: 15 Nov 2007
Posts: 58
Location: Sunshine State
FYI here is an animation of the action of this airgun, except mine does not have the built in regulator in the grip, it is just an empty chamber. also mine has an electric trigger with a solenoid hitting the sear.



I am seriously thinking of converting to a gas-operated action, much like the FX Revolution. But first I will try the closed bolt, blowback system, which is the first step to a gas-operated system anyway.

there are MANY animations of paintball gun actions here:
http://www.zdspb.com/tech/misc/animations.
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my DIY .22 cal PCP airgun 
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