Boyles/Charles law [discovered 1662] can be used to "ESTIMATE" the pressure drop as the charge leaves the 12 G. gaugemate and enters the forcing cone and 10G barrel.Boyles law states tha:P1xV1=P2xV2. This formulae can be transposed to:
P2 = [P1xV1]divided by V2
P1 = Breech pressure - 6000 psi V1= 12 G [.729]volume
P2 = Pressure as charge enters 10g barrel- UNKNOWN!
V2 = 10G [.775] volume.
Based on the following assumptions and applying Boyles/Charles Law I was able to "ESTIMATE" [or should I say guesstimate], that there would be a drop in pressure of 362 psi or 6% as the 12G charge enters the 10 G barrel.
Assumptions;
1/The 12 G shell generates 6000 psi on ignition.
2/The 12 G gas gas leaving the gaugemate has an average diameter of .752 as it passes through the forcing cone.
3/The forcing cone is 1.0 long.
4/The temperature of combustion was constant.
The reduction in pressure calculated would reduce charge velocity and thus recoil. But by far the greatest reduction in recoil is due to the difference in weight between the 12G gun and the 10G gun including the gaugemates.[ See my earlier post]
Last edited by Roy Hebbes; 10/17/09 03:14 PM.
