Zoogster,
good concerns.
I got 1000 each of mixed prepared once fired 45acp, 10mm, and 40 S&W brass.
The same load will always cause brass of a cartridge to fail within a 2% range of powder change. Every brand is within that range. The 45 Super and 460 Rowland brass also have the same strength as any other 45acp brass. The 45+P from Starline
IS a different design, and does have less volume. It has stronger case walls, but the same web structure.
I am not certain about pistol brass composition, but I am told that all rifle brass is between 3/4 hard cartridge brass and H06 tempered C26000 cartridge brass. Someone better at math than me calculates with Von Misses equations that Mauser case heads fail in the web around the primer pocket between 61,000 and 65,000 psi.
My tests show that the ultimate strength of pistol brass is consistent between brands as is rifle brass. Of course 6mmBR with a small primer pocket is good for very much more pressure than a .243 and 40 S&W is good for very much more pressure than a 10mm.
The part that capacity plays will never help 10mm 1.3" 200 gr catch up to 40 S&W 1.26" 200.
I would not bet high stakes that the 40 1.26" can alway beat the 10mm in an S&W 610 revolver, with a much longer OAL, where there is enough volume to help.
The way that the 40 1.26" 200 gr always beats the 10mm 1.3" 200 gr is that the 10mm case fails and the primer falls out, and the 40 can take way more powder without that failure.
I see kabooms in work ups, and they are always within 2% of repeatability, with controlled conditions.
One out of control factors to watch for is bullet squished to a larger diameter from compressing the powder. That can cause a big spike in pressure and primer or primer pocket failure with as much as 50% less powder than expected. Resizing the same loads will return the results to within the 2% expected range, if the only interference is the wider bullet in the case. If the bullet is too wide for the throat, the bullet is scrap. Ackley described this phenomena of large bullets working in a small bore without pressure spikes is documented in P.O. Ackley 1966 "Handbook for Shooters and Reloaders Vol 2" chapter 7
"additional pressure tests":
..30 cal barrel pressure barrel was fitted to the test gun, but the
neck and throat was enlarged to accept the 8mm bullet, with the bore
remaining the standard 30 caliber. A Remington factory 30-06 cartridge
with the 150 gr bullet had been tested and previously gave 57,300 psi,
for a velocity of 3030 fps. The the bullets were pulled from two more
Remington 150 grain cartridges and were replaced with 8mm 150 grain
bullets. To everyone's surprise, although the velocity was rather
erratic, these loads averaged 2901
fps, with a pressure of 40,700 psi.
And that is consistent with what I am seeing 40 years later with big bullets that swage easily with a flying start and pinched bullets that create a huge pressure spike.
There is also the problem of recoil, and a 40sw that makes 44mag power has real problems finding a slide heavy enough and a recoil spring assembly with enough force to prevent the slide hitting the frame too hard. High force recoil springs, in turn, require very fast magazine springs, which can be hard to load. Some disconectors cannot reset fast enough with stock trigger springs.
The problem is worse with 460 Rowland loads in small 45s, but there is not much for problems containing the 25acp at it's full potential. I know the P32 can shear off the hold open from radical recoil, and there is no place to put more springs.
What does it all mean?
Fix the case support, and, yes, the next problems in increased power start to appear. The 10mm large primer case is a fatal flaw that appears before any fatal flaws in the 40sw.
