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Tom West's Custom PC77 PumpMaster Classic Short Rifle



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My way may be too simple to be "right".

June 30 2012 at 3:32 PM
robert  (Login gubb33ps)
Crosman Forum Member
from IP address 68.105.50.68


Response to Gas velocity - port hogging relationship


Change the valve in some way, and the results will change, but if just looking at transfer port, can get an idea. Might be toosimplistic, but it seems to point in the right dirction for me.

So lets say you are playing ONLY with the transfer port.

Set your sweet spot velocity limit to whatever you choose, just keep the same strict limit for all transfer port sized tested. BEST would be a percentage limit...I tend to 3% of max.

Then it becomes the number of shots X the average energy.

Lets say we got the following 3% sweet spot with various sizes of transfer ports:

.07 = 35 shots @ 8 foot pounds = 280
.075= 30 shots @ 10 foot pounds = 300
.08= 25 shots at 13 foot pounds = 325
.085=20 shots at 16 foot pounds = 320
.09= 15 shots at 19 foot pounds = 285

That would lead me to believe the that at that pressure range, with that valve set up, a transfer port giving something in the 13-16 foot pound range is probably at its optimum. Change some other factor, like the operating pressure or the valve cycle, and would need to retest.

 
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