Survival style pellet gun build

[Kapcaniew]

Summer is coming. Time to arm up.
It's my first post on this amazing forum, and my first airgun build (other than sticking a compressor hose into a pipe and shooting sawdust ). I decided to pick a challenging task for this summer. I want to use this thread to ask for the oppinion of more advanced users, and later, hopefully, as a build log.

My idea is to build a smooth bore PCP airgun shooting 8mm bearing balls (or something of similar mass, 1-2g) at around 400-500fps (over 17j = permit required). Then comes the survival part: no access to compressors or air tanks - only hand operated. And now the challenge - I want it to look (and hopefully work) like a classic break action hunting rifle (because they're cool).

I'm thinking of using a coaxial tank, to leave some space underneath the barrel for a hand pump (maybe based on Gippeto's "Easy Stirrup Pump"?). I think a hammer valve would be perfect and easy enough to make without access to advanced metalworking tools - but I yet have to figure a good placement in a break-action system to be able to cock the hammer.
The design will be based on soft metals like copper and brass (easy to grind and easy to solder), aluminium (more durable and still easy to work with) and some mechanical parts made of iron ('cause I suck at welding and don't own a drill press). Also, I have a beautiful ash plank that's just begging to be turned into a stock.

I've seen many break-action airguns, but most of them were those crappy spring-pistons with a barrel that starts to wobble after a few shots. Are there any decent designs I could base my project on?
About the air supply: I don't think it will be possible to get more than 300psi from the hand pump anyway... Maybe I should go for 12g CO2 cartridges instead? That would make the whole build much easier. Also I don't really like the idea of putting the stock on the ground and working the pump with a barrel pointing right at my face...

Unfortunately, I won't be able to update the thread too often until July, as right now I'm struggling with my finals. As soon as they are over I promise I will live, eat and sleep next to my workbench

I'll be grateful for any advice and suggestions.

[mark.f]

I'm thinking of using a coaxial tank, to leave some space underneath the barrel for a hand pump (maybe based on Gippeto's "Easy Stirrup Pump"?). I think a hammer valve would be perfect and easy enough to make without access to advanced metalworking tools - but I yet have to figure a good placement in a break-action system to be able to cock the hammer.

Take a look at BtB's work in the pneumatic cannon showcase for some inspiration on hammer valves. As far the the break action, having the barrel push on a cocking "rod" when opened seems pretty boilerplate...

About the air supply: I don't think it will be possible to get more than 300psi from the hand pump anyway... Maybe I should go for 12g CO2 cartridges instead? That would make the whole build much easier. Also I don't really like the idea of putting the stock on the ground and working the pump with a barrel pointing right at my face...

A typical (Crosman) pump will exceed your specifications due to mechanical advantage, with more pumps required of course. You shouldn't have to work a pump with a barrel pointing at anything.


If I were you I would start from a base design such as the Crosman 1322, although the porting is a little restrictive. Gipetto could chime in on this a little more than I could.

Good luck.

[Gippeto]

Some thoughts, not knowing what your abilities are...

Linkage style pump will be more complicated to manufacture, but would be a really good idea. Crosman has/had numerous pumpers that could be purchased used/cheap and scavenged for required parts.

Would stay away from break barrel...sliding sleeve/breech as used on some of the Korean big bore rifles is simple and effective.

Would look into building a partially balanced spool valve, striker actuated. Barrel, breech, valve and striker could all be inline.

[Brian the brain]

You could go for an over under style with a QEV hooked up to the barrel in a Tee configuration, coming in from under the barrel.
That would make the breakbarrel easy.You could just swing the whole assembly down and open up the breech, while the barel, airtank and valves stay together as a unit,

That's what I had in mind for one of my guns...but the 1/2"QEV I use could be too bulky.

For 8mm however, you could use a smaller QEV.