SpudFiles

Uh, yeah. I finally posted it.

I wanted a general use and test platform pneumatic so I made this. I have some experimental data at the end which I compared to GGDT predictions as best I could. The results lined up quite well and I believe most of inaccuracies were the result of my human-error in pressurizing the gun accurately and consistently.

Video link (with obligatory death metal, of course)


Note for D_hall:
I tried using your valve flow coefficient calculator, but it got through the first couple data sets then got stuck in an infinite loop for some reason.
Also kudos for making this thing so damn accurate. Tweaking the numbers sightly can get near perfect data alignment, but I believe the ones I used are the most representative of my gun.

Specs on the gun:
Chamber: 30 cubic inch
Barrel: 1.05" x 23.75"
Valve: 1.05" porting piston valve
Piston travel: about 1"
Piston mass: 98 grams
Pilot: 1/4" ballvalve

Maximum muzzle energy: ~160 Ft-lbs (217 J) with a 31 gram projectile, 160 psi

Very nice! Looks like a nice chunk of fun! Anything in particular you will be testing with it? Oh and the bacon was a nice touch, but you should have gone with tactical bacon

Bacon!

I like the piston support.

Also, quite impressive energy levels for a pneumatic. With a 30 gram projectile in a 2 foot long 0.75" barrel with 12x in a 30mL chamber I got around 310 fps.

nice video. The death metal was rather... metal-ly.

Very good test! I love to see a good GGDTvsReality test.

I also like your piston design, very neat and looks efficient.


(U mad?)

After having skimmed through this, now I had a good look:

a) lolol @ the trollfoot

b) shooting liquid targets indoors. Wonderful

Anything in particular you will be testing with it? Oh and the bacon was a nice touch...

Probably just some small penetrator rounds for now. It would be interesting to see how much steel you could punch through with only 200J
Nice touch? It's the bloody scale! Derp!

Very good test! I love to see a good GGDTvsReality test.

Some day I'd like to do a HGDT version, though burst disks would probably be the limiting factor.

b) shooting liquid targets indoors. Wonderful

There was a live 240volt plug right behind every one of those shots, and it got pretty well saturated... with me still walking around in the water. Microwave oven transformers, however, still scare the crap out of me.



Edit, oh and fun fact from the video:
In the first shot you can see the projectile bouncing back, and that particular trajectory gave it a hilariously perfect flight path toward my head, at maybe 20-30 fps. but luckily I managed to dodge it.. all those years of unreal tournament are finally paying off

Little penetration test for sh*ts n' giggles.

15 gram chunk of round file vs. 0.130" (3.3mm) mild steel. Technically made it through, but the 'exit' hole is only about 1/16" wide

The ducttape sabot weighed an additional 15 grams and separated on impact, so this was only the equivalent of 75 ft-lbs (~100) joules of kinetic energy against the target.