When I have shot light balls like the ones you show there, always one side has caught the barrel more than another, so it generated random spin in one direction or another, making it absolutely useless. Easy fix to that is making a hopup for the balls to control spin, which I'm sure david knows about

depending on how much variation your barrel can take, I'd suggest unpopped pop corn kernels

as for cheapest 6mm bb's your best bet is going to be the cheap walmart variety

Once again thanks for the links

If I ever get a day off work, I'll be attempting my build finally

Thanks for the link, big help looking at it

I had one more question though, anyone know how fast a standard pop off valve would exhaust at ~90psi

Working out an idea in my head and wanted some advice before I'd built anything Working on a piston, air flow would be coming in through a schrader valve Could you use a Safety valve as a sort of semi-auto device? Fill the chamber to the safety valves pressure. Safety valve blows, piston comes back ...

First of all I've been reading up and looking around the site and it's given me a few ideas here, but none of them are viable without some form of gas, which leads me to my questions. Assume I'd be using a vortex cap in my design, looking at ~60 inches of barrel, a few thousand rounds in the ammo bo...