I've experienced that same problem using a 1.25" T (3/4" porting) and triggering with a blowgun. I had a spring in mine rather than a bumper, but my friend's gun (2" tee, 3/4" porting) had no bumper or spring and still bounced if he swung the ball valve fast enough.

I think I ended up making the ...

This is a cool idea! I really like it.
@Twitch: way to go ... ouch!

You can't really get consistent triggering just by pulling a blowgun trigger or ballvalve. You might arrange a hammer valve, which is what I was thinking of, or you might have a pseudo-hammer valve, where your hammer hits the little button on the blowgun valve. A direct hammer with a schrader valve ...

yeah, this is a good topic, it's something I've been wondering about. If you look at it from an energy perspective, you have KE=1/2*m*v^2. Then you also have E=f*d. So the higher your energy is, and the less force your projectile has to produce to penetrate (ie, make it sharp and keep the diameter ...

I'm really, really curious about how you get more than one shot per tank. That method would pretty much enable an amateur to build something like a pcp rifle. The trick has to be with your triggering method, because it's not like a qev is anything special. I've observed multi-shotting from two ...

@Spudblaster: I don't know why you don't get any changes. Where do you get your iron oxide? Do you melt your sugar propelant, or pack it as a dry powder? I don't think that should effect it, but it might.

Ok, so you're using a precipitation method instead using KOH and letting the ammonia boil off ...

Very nice! That's a sweet sight, too. I'm curious about how you made the suppressor so effective. Have you tested it w/ and w/o to hear the difference?

Also, I'm confused about how your piston works. It looks like the gun is a coaxial. I assume the air pressure is only on the left side of that plug ...

Well, kudos on the conversion process! I'd like to hear how you do it. I've tried making sodium nitrate using NH3NO4 and KOH, but since all the compounds involved were very water-soluble, I could seperate them. How do you dry the KNO3 when you are done?

Actually, iron oxide is pretty much ...

Ok, in case anyone is wondering, Fe203 is indeed a catalyst. You are right that it doesn't decompose, but it doesn't have to to be a catalyst. It would only have to decompose if you wanted it to be an oxidizer, which is what happens with thermite. It works admirably as burn rate catalyst, it can ...

@joanna: dude, whoever thought your jack-hammer action up needs to be congradulated! That's slick. All the advantages of a bolt without the flow restriction of blow-forward or the woes of the blowback. Would you mind starting a thread on that thing?

@Jack: what exactly is causing the low power ...

thanks for the link Jack, I knew I'd seen it somewhere on here but I couldn't find it.

*sigh* The point of having the bb's sucked forward is that I'm not going to let air into the rear of the barrel: I tried to show it in the diagram, that end is plugged. The only air coming into the barrel is ...

Ok, you guys aren't getting it. I based the whole thing off this gun:
http://www.spudfiles.com/forums/bv150gbmg-t6826.html

The principle is that the air comes into the barrel/mag through that hole(s) which is smaller in diameter than your bb so it doesn't fall out. The bb's get sucked out of the ...

It's really quite simple. I drew up the basic thing w/o the 1/2" PVC housing I actually would probably use if I built it. Let's see if this works:


Edit: hooray, it does! It's kinda grainy, though, but I guess that ought to do.

Thanks!

Yeah, I blew up a bottle one time. Well, it broke where I had the schrader stuck through the bottom of the bottle, and I thought I'd blown myself up, but then I was like "whoah, I'm still in one piece, how did that happen?"

I had a crazy idea for a dirt-cheap plastic soda bottle bb strafer. Have a 3' barrel with the breach end epoxied closed, a few small holes drilled in the barrel about 1' from the breach end to let the air in. then glue the barrel in thru a hole a bottle cap, so that the air holes are just inside the ...