CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.
John0011 said:
So basiclly the Vihtavuori 45 acp loading in CIP is a 45+P loading in SAAMI.
No. The measuring systems are not directly comparable like that. I've observed the conformal system tends to yield higher numbers as case diameter increases, so the ratios you find for 9 mm will not apply to 45 Auto size cases. For example:
.308 Winchester and .223 Remington both have copper crusher Maximum Average {peak} Pressure (MAP) values of 52,000 CUP. But measured by a conformal piezoelectric transducer, the .308 Winchester has a MAP of 62,000 psi, while the .223 Remington MAP measures only 55,000 psi. Those numbers are arrived at by taking the same reference loads used in the copper crushers and measuring them in the conformal transducers. They do not represent real changes in pressure value.
For the .45 Auto,
the SAAMI MAP is 21,000 psi (or 18000 CUP by copper crusher). The
CIP .45 Auto MAP is 1300 bar (18855 psi) by channel transducer (formerly, and now considered obsolete, 1400 bar (20305 psi) by copper crusher). So the SAAMI transducer reads higher than its copper crusher and the CIP's channel transducer reads a little lower by copper crusher. In both cases the methods and gas sampling points are different. There isn't a lot of value trying to apply conversion factors as they all seem to be accurate to about ±15% or so, which isn't very useful).
I took Gordon's Reloading Tool and had to create the 200-grain HAP in it, but I did and the result is about the same as the lead RN load I came up with before, with the HAP seated to Hornady's recommended 1.23" COL and assuming 26.0 grains case water overflow capacity, it says 9.5 grains will put you in the middle of the upper load range (around 25,000 psi) which I stopped at to be a little conservative. Even so, you can see the software sounded warnings, which I take to mean, work the loads up in the steps shown to be conservative and keep an eye out for pressure signs.
Again, be aware these are simulations and not the result of actual testing, so YMMV. However, I note that with Vihtavuori's top .45 ACP load of 7.4 grains of 3N37 under a 200-grain bullet, seated just slightly shorter, the measured velocity is 910 fps from a 6" barrel, while QL predicts 930 fps and GRT predicts 971 fps. This suggests the pressures and velocities in both programs are on the high side, tending to make both graphs conservative. Just remember, your lot of powder, your primers, and brass, and the tightness of your chamber and bore are different, so you can't count on this to be true. It is just an estimate with a significant variation from reality being possible.
You see several pressure traces under the top one, and these are reductions in increments of 0.3 grains, as the numbers immediately across the top of the graph show. Because powder peakiness can often be greater in handgun charges than in rifle, Western Powder recommends taking 15% off maximum as a starting load, or 8.1 grains in this 3N37 case and 9.8 grains in the 3N38 case, so these plots don't go quite low enough. Nonetheless, you can eyeball that these would produce about 800 and 820 fps in the two powders, respectively, with a 5" tube.
