Looking over data booklets I have had for decades, I always love to see how max charge weights go up and down over time using the same components.
Yes, what was considered max may have changed, and CUP vs PSI is a factor, but when I find a very drastic difference that can not be explained, I wonder what is going on. A very glaring example.
My circa 1995 Hercules booklet lists a 125 grain FMC load using Unique, as does my 1996 Alliant booklet that was the first from Alliant, and the current Alliant website also lists a 125 grain FMC/Unique load as well. All sources list OAL as 1.15", barrel length 4", and WW small pistol primers. Now here is where it gets interesting. Although we do not know the exact diameter or type of FMC bullet used, we do know its weight, and the listed max charges for Unique are listed with their corresponding pressure in psi as follows:
1995: 6.2 grains 1170 fps 31,300 psi
1996: Same
2007: 4.9 grains 1077 fps 31,745 psi
Hmmm, Alliant tells me that Unique has the exact same performance spec as it ever has (even the "improved" version) when I asked about this data anomaly, and from tests I have seen comparing the two this would seem accurate. Yet when comparing psi-to-psi using identical components, and only the charge weight changes, 1.3 grains less of Unique in today's world has higher pressure??? This is a very substantial charge weight difference that lot-to-lot variation can not come close to explaining. The velocity drop looks very plausible, but the increased pressure???
I asked them if it was possible that the propellant they used for this Unique data may have actually been drawn from a recalled batch where Bullseye was accidentally put in the 8 lb drum instead of Unique, but was told no, and that the data is accurate??? Other than a CYA for legal reasons, what do you think could explain the data?
Yes, what was considered max may have changed, and CUP vs PSI is a factor, but when I find a very drastic difference that can not be explained, I wonder what is going on. A very glaring example.
My circa 1995 Hercules booklet lists a 125 grain FMC load using Unique, as does my 1996 Alliant booklet that was the first from Alliant, and the current Alliant website also lists a 125 grain FMC/Unique load as well. All sources list OAL as 1.15", barrel length 4", and WW small pistol primers. Now here is where it gets interesting. Although we do not know the exact diameter or type of FMC bullet used, we do know its weight, and the listed max charges for Unique are listed with their corresponding pressure in psi as follows:
1995: 6.2 grains 1170 fps 31,300 psi
1996: Same
2007: 4.9 grains 1077 fps 31,745 psi
Hmmm, Alliant tells me that Unique has the exact same performance spec as it ever has (even the "improved" version) when I asked about this data anomaly, and from tests I have seen comparing the two this would seem accurate. Yet when comparing psi-to-psi using identical components, and only the charge weight changes, 1.3 grains less of Unique in today's world has higher pressure??? This is a very substantial charge weight difference that lot-to-lot variation can not come close to explaining. The velocity drop looks very plausible, but the increased pressure???
I asked them if it was possible that the propellant they used for this Unique data may have actually been drawn from a recalled batch where Bullseye was accidentally put in the 8 lb drum instead of Unique, but was told no, and that the data is accurate??? Other than a CYA for legal reasons, what do you think could explain the data?