schmanman's steel piston bb rifle

[schmanman]

This is my piston rifle. It easily shoots a slingshot BB through plywood or a can or two (those are slingshot bb's in the last two pics) at 155 psi. the piston is a rear foot peg off an old dirt bike, drilled out, and sanded with fine emery cloth. the chamber is a ten inch long section of 3/4 inch diameter galvanized steel the elbow and tee are made specifically for pneumatics. the barrel is 2 feet of 1/4 inch diameter copper. It is extremely accurate. the pilot vent is a blowgun. the gun pumps up to 200 psi with 15 pumps of the bike pump, because of the small chamber. the highest I have taken it is 250 psi, and the BB is going so fast that you can rarely see it. I will add a scope, co2, and a flat black paint job. this thing is SOOO fun!!!
(oh yeah, you grab it between the tee and the elbow and hold it like a rifle, with your other hand in the back on the blowgun) pimpmann, can it still be entered in the contest?


an overview of the gun.


above is the tee, made for pneumatics.


the air chamber.


the barrel, and some slingshot bb's.


the chamber, barrel, and some slingshot bb's

[saladtossser]

looks like something i would enjoy, how do you make a piston valve out of steel fittings? i'm stumped on how you got the thing to stick through a bushing like that

[ProfessorAmadeus]

Very cool! That is an awesome Gun! What does the piston look like and how fast does the blpw gun triger it? I want to see some damage pics to see the full power of it and try and get it to a higher psi
Is that treaded piece the piece that the piston seals on?

[COD_FILLETS]

Can you post a diagram/plans of how/what you did?

[SpudStuff]

Don't ask for plans. If you cant figure out how to build it from the picture you shouldn't be building it.

Nice gun you should paint it black and red and add a hopper for BB's.

[saladtossser]

Don't ask for plans. If you cant figure out how to build it from the picture you shouldn't be building it.

I think that doesnt apply to things with hidden moving parts...

[)DEMON(]

I see these metal barrel sealing cannons are becoming popular.
Very good work, you have done an excellent job. You always manage to find things to use in your cannons.
Like I said befor, you will get better preformance with a ball valve exhaust.

[MrCrowley]

yeah but blowguns are way cooler b/c they have a trigger...unless you hook up a spring activated ball vlave.

[schmanman]

thanks!

the bushing is threaded, so I tapped it so there were threads all the way to the bottom, then Teflon taped a nipple, and screwed it into the back. now I can screw on the barrels. and since all pressurized parts are steel, this thing can be taken to extreme pressures.

I am working on the ball valve exhaust. I will use a 1/2 inch ball valve I got for free. this whole gun cost me nine bucks (barrel and brass fittings to hold it on). look for more of these from me, because my grandpa has a huge bucket of galvanized parts.

The piston is about an 1 1/2 inches (I'm bad at estimating, so I am probably off) long, aluminium, with the front nearly smooth, and a hole drilled in the back to increase the surface area, and reduce the weight by half. It seals on a piece of surgical tubing sleeving the 1/4 inch pipe going through the bushing. the piece of surgical tubing is folded over on the top, to create a nearly perfectly flat sealing face. the piston may or may not be replaced by one machined on a lathe in the future.

[LucyInTheSky]

I like the way you have made and over-under but put the chamber facing the other way.

You probly shouldnt use a ball valve as an exhaust as it wouldnt fell right opening one, unless you used one as a trigger like in my sawn off and brians.

congrats.

also do you prfer this one or your big one?

You could put open sights on it also, it would make it even more accurate.

[COD_FILLETS]

Don't ask for plans. If you cant figure out how to build it from the picture you shouldn't be building it.

I think that doesnt apply to things with hidden moving parts...

I was implying what saladtosser said. I dont know if its just me, but I cant see through metal very well.

[SpudStuff]

Your piolt volume seems to be very large. If you decreace the volume you should notice an increace in performance.

[LucyInTheSky]

One thing you could do (just for looks not performance) make the fill point face down instead of sticking out to the side.

His pilot volume isnt to big as it is thin pipe anyway, dont change it as it looks good the way it is.

Also what muzzle volocity you getting? I think you said you had a chrony

[schmanman]

I suspect the muzzle velocity is very high, because It shoots through a steel can easily, embedded a nail an inch and a half into a wolmanized 4x4, and the bb has very little mass, so the velocity has to make up for that. My uncle has the chrono. spudstuff, the pilot volume was kept small, The piston takes up most of that space. the schrader valve is over to the side so I can easily hook up the compressor. I do not really prefer one cannon over the other. oh, and the filling point (schrader valve) is on the side like that so I can easily fill it up with my compressor, and so I can set it on the ground when filling it with a bike pump, and the fill valve is still angled up in the air.

where's brian the brain? I really would like some feedback form him *wink wink, nudge nudge*

[POS]

Seems like a nice gun. You should add a stock, of you are going to use a scope. Not much use for a scope when you can't hold the gun still.