DD,
Thank you for the "thanks".
I would agree that your 37 gr. load in current brass would be a fine load under a 250 gr. bullet. For those who want to load the full 40 gr. into a modern case, Swiss b.p. is the answer. It is 10% more dense than Goex and, thus, a 40 gr. charge of Swiss will fill the case to a little less than the same level that 37 grs. of Goex will.
One wonders how Goex loaded 42 grs. of their powder into a .45 Colt case(??)......must have used a heap amount of compression! Interestingly, the ballistics are sub par for that amount of powder used. http://www.goexpowder.com/load-chart.html
One of the smokeless powders I like in the .45 Colt is Herco. 9grs. gives 910 f.p.s. at 12,600 c.u.p. according to Alliant.
The pressure / velocity data for the .45-70 taken in the Lyman ballistics lab clearly shows that the proper smokeless powders are on par with b.p. regarding velocity / pressure. The .45 Colt cartridge is a different cat, so to speak and I agree with your assessment of approx. 9,000 psi with 37 grs. of Goex. 40 grs. of Swiss will increase that, and the velocity as well.
Regarding the time / pressure curve, my thoughts are that the b.p. wiill give a sharper initial spike, otherwise, I am at a loss to explain why b.p. will bump up a soft lead bullet, whereas, smokeless powder won't. That has been my experience.
Interestingly, I ran a test a few years back in the .44-40 using a rifle with a 21" barrel and another with a 24" barrel.
Note the higher velocity increase with both 4227 & RL7 powder as compared to b.p. which would indicate that they would have the flatter pressure curve.
40 grs. Swiss FFG - velocity increase 19 f.p.s.
21" -1,273 f.p.s.
24" -1,292 f.p.s.
16 grs. H4227 - velocity increase 58 f.p.s.
21"- 1,177 f.p.s.
24"- 1,235 f.p.s.
25 grs. RL-7 - velocity increase 109 f.p.s.
21" - 1,258 f.p.s.
24" - 1,367 f.p.s.
Testing in 2008 with pressure trace equipment using my .45 Colt '94 Marlin Cowboy rifle will give us some accurate information. Stay tuned.
Regarding primers: Mercuric priming was used in the first b.p. cartridges. They were hard on brass, but not barrels. Then, in the early 1900's, priming compound containing potassium chlorate entered the picture. These were corrosive primers which could ruin a barrel in short order if it was not cleaned properly. Remington "Kleanbore" priming introduced in the mid 1920's were the first non corrosive primers. Winchester followed 5 years later with their "Staynless" brand of primers.
To your point, yes indeed, if one fired b.p. cartridges with the corrosive primers and didn't clean the barrel properly, bad news, and as you said, b.p. could be incorrectly blamed. Not too long ago, after firing b.p. cartridges in my .357 Marlin, I didn't clean it for over a week. When I did there was no sign of corrosion at all.
Sincerely,
w44wcf