Quote:
Originally Posted by pinkymingeo
Every now and then I see claims that 4756, when loaded above current specs, gives high velocities at lower pressures. Where does the pressure data come from? Not from current loading tables, certainly. Has somebody paid for lab tests?
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In my testing with SR4756 I relied on the manufacturers data from their website.
Hodgdon - The Gun Powder People. I was initially drawn to the numbers for the 40S&W 180 grain loads. I noticed that among all of the Hodgdon offerings, 4756 produced the highest velocity with the lowest pressure. If you check you will find they report 1,018 fps at 28,800 psi for 4756. The highest claimed velocity with the 180 gr load is 1,053 with a pressure of 33,200. It seemed to me that increasing pressure by about 5,000 psi for 35 fps increase in velocity was not desirable.
With my .45 ACP I loaded a 200 gr LCSWC over 8.2 gr of 4756 and clocked an average of 964.2 vs. Hodgdons claimed 966. I think that is pretty close. My cases showed no evidence of excess pressure. There was no apparent blow by and the primers were not flattened or cratered. That would lead me to believe the loads are really not pushing the envelope. I have no reason to test my theory and in fact found the 7.8 and 8.0 loads actually grouped better.
I hope that helps to clarify.
FranK