SpudFiles

Something I've been pondering, a .30 cal pump pistol based on the Crosman 1322, so I put a couple of potential variations to pixels approximately to scale (10 pixels = 1mm)

In both cases the hammer valve is replaced by a piston that is slightly biased forward.

The second one has a bit less volume but has less o-rings... and in any case, still vastly more volume than the original, pumping would be a chore... in practice I would aim for around 4 cc.





Some very rough calculations suggest around 450 fps with a 45 grain pellet from a 12 inch barrel would be achievable with something below 25 pumps.

It is an upgrade that uses a piston valve and not the hammer system, is what I understand. I really like that weapon and I had planned to buy it but they don't exist around here, at least for a long time, when I had the intention of doing so.
A question that is interesting, to improve these weapons is to spend only part of the pumped air. I mean, with a small auxiliary tank, if you pump 30 times, and you generate 50 bar, when you make a shot you only spend 5 bar, and then you only pump let's say 10 times to replace the 5 bar, which wasted the shot, but not from 0 bar. The numbers are random as an example, it is just to make me understand. otherwise, I like that piston valve better than the traditional hammer system. It seems, at first glance, simpler.
ah ... by the way, the drawings are beautiful!

Straaaange timing, both this post and me happening to check my "Spudfiles" label in gmail. The 1322 I want to "breathe on" is in the mail right now. (along with a steel breech and longer barrel) I still have to source the 1389 pump handle for a "1389 clone" (which was difficult in 2008, I can't even imagine now) and a blued-steel hammer-spring plug (maybe).

I think the second diagram (even if it does cut down on chamber volume) would be much, much easier to build. That back part of the first valve looks like you would have to build a valve body that threaded together to get the piston in.

Any plans to use a stock? I'm about tired of the 1399 plastic stock (even though I got one to use) so I was thinking of making a folding/collapsing wire stock for what I'm doing (kind of a backpack gun).

Are you using a smoothbore or rifled barrel? I know they're 0.50 cal but maybe you could roll your own version from an insulin needle or something?

I, for one, would be terrified of ketamine darts...

hectmarr wrote: ↑

Tue Feb 09, 2021 9:59 am

I really like that weapon and I had planned to buy it but they don't exist around here, at least for a long time, when I had the intention of doing so.

Yes, the 13XX and 2240 series are probably the most popular and modified air pistols in history.

A question that is interesting, to improve these weapons is to spend only part of the pumped air. I mean, with a small auxiliary tank, if you pump 30 times, and you generate 50 bar, when you make a shot you only spend 5 bar, and then you only pump let's say 10 times to replace the 5 bar, which wasted the shot, but not from 0 bar. The numbers are random as an example, it is just to make me understand. otherwise, I like that piston valve better than the traditional hammer system. It seems, at first glance, simpler.

I agree that dump valves that empty the whole chamber are inherently wasteful. In this case however, I wanted a larger volume of air in order to give good power with the larger caliber, and the hammer valve takes up too much space.

Ordinarily however I would be a vocal advocate of using a "timed" valve instead of a dump valve

ah ... by the way, the drawings are beautiful!

Credit goes to Gil Irvin who's drawings I modified:



Note how tiny the original chamber volume (in blue) is...

mark.f wrote: ↑

Tue Feb 09, 2021 11:14 am

Straaaange timing, both this post and me happening to check my "Spudfiles" label in gmail. The 1322 I want to "breathe on" is in the mail right now. (along with a steel breech and longer barrel) I still have to source the 1389 pump handle for a "1389 clone" (which was difficult in 2008, I can't even imagine now) and a blued-steel hammer-spring plug (maybe).

Great minds... or perhaps given the ubiquity of the platform, statistical inevitability

I think the second diagram (even if it does cut down on chamber volume) would be much, much easier to build. That back part of the first valve looks like you would have to build a valve body that threaded together to get the piston in.

I agree, though in either case a multi-part valve body is necessary in practice.

Any plans to use a stock? I'm about tired of the 1399 plastic stock (even though I got one to use) so I was thinking of making a folding/collapsing wire stock for what I'm doing (kind of a backpack gun).

No, I still have a 1400 lying around that will probably be the next big-bore candidate if this works.

Are you using a smoothbore or rifled barrel? I know they're 0.50 cal but maybe you could roll your own version from an insulin needle or something?

.30 cal rifled barrel from a firearm, I've collected quite a few in various calibers for just such projects...

I, for one, would be terrified of ketamine darts...

I'm guessing you had missed this one? viewtopic.php?t=26708

jackssmirkingrevenge wrote: ↑

Tue Feb 09, 2021 11:23 am

I'm guessing you had missed this one? viewtopic.php?t=26708

I DID, nice.

Also lol at hectmarr's last post.

mark.f wrote: ↑

Tue Feb 09, 2021 11:47 am

Also lol at hectmarr's last post.

You can see what happened, to tame is "domar" in Spanish so an easy leap to make when English is not your first language

Yes, I think the solution of the second drawing is simpler, even if you lose a little air volume, which compared to the original small air volume, is much more