From my collection: W-W lab data on three, different 12 ga factory loads: 700 psi @ 26"; 620 psi @ 28" and 605 psi @ 29".
Just for grins, a model that assumes PV = constant (a slightly pessimistic or high assumption) indicates that Sherman Bell's 12 ga, 1 1/8oz Bi, smokeless-for-black load would have shown 700 psi at 30", had Sherman wasted a pressure transducer there.
Considering calibration issues (fraction of full scale and all that) I wouldn't bet on these being very precise -- maybe +- 100 or 200 psi????
Last edited by Fred; 12/05/06 09:03 PM.
