The Firing Line Forums - View Single Post - Signs of pressure in 45-70

SL1 · May 5, 2012, 09:00 PM

And I find different companies holding the 1895 Marlin to WIDELY different pressure limits for the .45-70 cartridge.

The highest NUMBER that I found was from Barnes, with a stated limit of 42,000 psi. But, they also stated that the SAAMI pressure limit is 28,000 psi, rather than 28,000 CUP. So, it isn't clear to me if they were using CUP or psi for the actual measurements. I also found that Speer is limiting all "modern" .45-70 data to 28,000 psi, and the "Trapdoor" data to more like 20,000 psi. Hornady makes the mistake of saying that the use of the .444 Marlin in the same gun makes it OK to load the .45-70 to 40,000 psi. (But, my exmple in the previous post illustrates why that is not an appropriate basis for 40,000 psi in the .45-70 cartidge.)

Anyway, I can see why the OP is asking questions. The "pros" seem to be all-over-the-map on this particular cartridge/gun combination, and some of the logic that they are providing in print seems questionable, too.

SL1

SL1

May 5, 2012, 09:00 PM	#13
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	I just looked at my variious manuals And I find different companies holding the 1895 Marlin to WIDELY different pressure limits for the .45-70 cartridge. The highest NUMBER that I found was from Barnes, with a stated limit of 42,000 psi. But, they also stated that the SAAMI pressure limit is 28,000 psi, rather than 28,000 CUP. So, it isn't clear to me if they were using CUP or psi for the actual measurements. I also found that Speer is limiting all "modern" .45-70 data to 28,000 psi, and the "Trapdoor" data to more like 20,000 psi. Hornady makes the mistake of saying that the use of the .444 Marlin in the same gun makes it OK to load the .45-70 to 40,000 psi. (But, my exmple in the previous post illustrates why that is not an appropriate basis for 40,000 psi in the .45-70 cartidge.) Anyway, I can see why the OP is asking questions. The "pros" seem to be all-over-the-map on this particular cartridge/gun combination, and some of the logic that they are providing in print seems questionable, too. SL1 SL1