But they seem to consistant in the way they are spraying.
this is a c02 or pcp setup? Liquid c02 not getting into the valve is it? I would start checking everything, and would begin with a stripdown, if you can handle it. You are saying it will do 2-3 stacked, and then 4 and five are off and to the left/right.
Chrony it. If nothing is moving around, you should see a velocity difference on the chrony.
Crosmans from a tin? IF so, get a Mic out, and sort by 1000ths. I have had Crosmans come out from .215 to .219 from the tins. BIG difference out of a barrel that might prefer a little larger of a pellet....
Nothing is clipping them when they are going into the breech area?
I would dismantle and make sure everything is clean. Check seals. Check seats. Make sure something isnt happening weird every 4-5 shots, like a valve stem/seal canted and rotating. while your at it polish it all, striker, spring ends, clean the tube, etc.....
Lap the bore while off, with some valve lapping compound, and touch the crown up. Reassemble, making sure you have a good transfer port seal.
Dont put the muzzle break back on yet...
Sorry I can't offer more than basic troubleshooting, but sometimes when somebody mentions something, you say "oh man, I forgot to check it"
Good luck and hopefully someone else will chime in and help.
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