Spudtech Forum

Brand new at this, built a pneumatic gun with 12 ft of joined rifled (rifling is indexed and matched) 1.5 inch sched 40 PVC barrel. Mechanics of gun working well but am having trouble with spud ammo breaking up outside the barrel. Have used idaho russets and yams which I precut with a long chamfered section of 1.5 PVC, then trim to length and carve conical tip. Fit in barrel is snug but not overtight, firing at pressures of anywhere from 60-90 psi (plan to go up to 125 once I get my ammo to hold together). Anybody have any suggestions?

I have notice some people say they can't get the potatoes to stay together, but i have shot them out at 140psi and they stayed in one solid piece. I do not cut them at all, because i do know the skin helps keep them solid. My barrel is 2" barrel with a 1 1/2 modified sprinkler valve attached to that. what fittings do you have connecting the barrel to the valve? maybe one of the holes is really small and that much force through a small hole will cause the potato to crumble on impact from the air. Let me know and maybe i can try and help.

Hmm so just to get this right you have a 12' x1 1/2" barrel on a pneumatic? If so I would first cut it down seems a bit much. Even my largest cannon which is a 3" barrel with a 6" combustion chamber is only 8' long. I wonder if this might be the problem not sure why but Its a start. My 2" pneumatic with mod sprinkler valve fires at 110psi and will chuck a spud at least 100-120 yards (never ran the tape to see)

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Spud gun list as of 2014
-Best: 4" PVC chbmr 2" barrel, breach load, combustion heptane/ether, longest range 362yd
-Largest: 6' PVC chbmr 3" barrel, breach load, combustion heptane/ether, longest range 128yd

Have you tried a type of wadding or a patch? Old field guns used a wadding behind the projectile and muskets use a patch to make a better seal. So maybe a patch made of paper or Walmart bag plastic might help. Or maybe a wadding behind your spud would help. Crumble up a piece of newspaper to ram before the spud to cushion the force of the air.

Swiat has a point. A sabot would help. For 1.5 inch PVC, try using a blue plastic cap from a milk jug. I don't know how it will work with rifled PVC though. The paper may be your best bet.

Is there a gap where you joined the barrels?