Would this work???

[Doctore]

I was thinking about this recently.It is simple but i dont know is it efficient.
Is there anything similar to this,if so please tell me.I might build something like this,but i dont know is it powerful enough.

http://imageshack.us/photo/my-images/706/unledlwy.png/

[Gun Freak]

Is it supposed to be semi? If so, it won't work, because there would be so much pressure on the piston that the rubber bands wouldn't be able to reset it and it would just vent out on shot one. If it is supposed to be single shot then it would work if you could work out the trigger system but most likely you wouldn't be able to make one strong enough to withstand the enormous pressure from that wiiiide piston. It might work if your piston had a smaller diameter though. I don't think it is worth making though. It would probably be powerful but wouldn't be worth the trouble when you could just make a piston valve or something.

[Doctore]

It is supposed to be single shot.I know its better to make a piston airgun but its cheaper for me to make this.

[Gun Freak]

Oh ok well it will work for single shot but good luck making a strong enough trigger system...

[al-xg]

JSR made a similar contraption a while back, quite a bit smaller though.

You could have a T on the end of the chamber and use a much smaller piston that slides inside the T.

But to be honest, I reckon that getting this to work properly, wouldn't necessarily be any easier or cheaper than a QEV or QDV, or even a spring loaded ballvalve...

[Doctore]

Well parts are expensive and they are not well molded in my country,but i have made a piston valve airgun several times.I always loved real looking airguns so trigger assembly is one of the reasons.

[jackssmirkingrevenge]

JSR made a similar contraption a while back, quite a bit smaller though.

Same concept, different geometry.