SpudFiles

I'm developing a CO2 powered sniper rifle for marbles, I have a really good design going so far, but I'm wondering if anyone has any bright ideas on some good ways to make it so each time i load a marble into the barrel it won't roll around. The way i will be loading marbles is from a tee in the barrel with a sliding bolt on the inside opening and closing the top of the tee. I looked at my paintball gun's anti-double feed mechanism but it will be difficult to replicate that working mainly with PVC. Anybody got any ideas? I'll donate spudbux to whoever gives me an idea that i decide to use . Pictures would be great too. Thanks!

you could put a small ruber flap in the barrel just enough to stop the marble rolling around and it could act as a hop-up as well making the marble spin.

Put a small bead of rubber glue on the top and bottom of your barrell, Rubber glue is the stuff used to repair bike tires.

screw some paintball detents in it

The spring would be stiff enough to stop the ball from rolling over it but not to stop it from firing.