SpudFiles

I have heard that 3" fitting fit in 4 inch pipe for pistons or gluing. Would this also work for ammo(would it work if it was sanded down a little)? Would 2" fitting be used for the same purposes in 3" pipe? Would any pipe/fittings fit as ammo in three inch pipe?

I don't know why you would want to shoot fittings, but yeah you can get them to fit in every situation you described.