SpudFiles

Well,I just sketched this and as you can see the trigger mechanism is not ready,but I hope that you will understand how it works. Would it be possible to shoot 5-10shots with 5-10Joules of kinetic energy with marbles?The chamber is 1Liter and pressure is 8bar.

it will work but won't have too much power. It will also fire very inconsistent.

"it will work but won't have too much power"? I understand but how can I make it better?Suggestions

Gunner wrote:"it will work but won't have too much power"? I understand but how can I make it better?Suggestions

Raise the pressure?

Be careful though.

Raising the pressure helps, as does using a weaker spring behind the valve. You can also manipulate how long the valve opens by using a heavier hammer or a stronger spring to propel it. The more air you can let escape, the stronger it will shoot. At the expense of number of shots of course.
A fairly large chamber pumped up to 200-350 psi would probably give you a nice repeater.
Keep in mind that a hammer valve tends to self regulate to a degree. As the pressure drops, the valve is naturally less resistant to being opened and more air will escape. Some consistency can be expected from the shots in the middle of the series.

Valid points but I think a 1 litre volume is still too low, I would go for at least 3 times that amount.