With a 15.9 grain JSB Jumbo I'm at 14 FPE now (634 FPS). My adjustments are maxed out. I also want to start with a 2600 PSI fill pressure as that seems to be where the grouping tightens up (higher fill pressure seems to cause a slight scatter effect). Is it a combo of a stronger hammer spring and a slightly larger transfer port? I figure just a larger transfer port. Am I in the right direction?
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