Powder burn temperature

[LongPoint]

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[9.3X62AL]

Welcome aboard, Long Point. I do about the same thing with my 357/41/44/45 revolvers you describe--231, Unique, and 2400 as pressure/velocities escalate.

I don't really have an answer for your heat-related question. I have seen as a result of forensic testing that ball/spherical powders imprint spherical stippling on the bases of both jacketed and lead revolver bullets, and that rod-type powders (IMR-4227 in the test I saw) left impressions that were a little more granular. What effect heat had to do with this is conjectural to my mind and its social-science-major education, but it was clear to me that the boolit bases were exposed to some tremendous pressures. This does not only apply to magnum handguns--the Cal-DOJ lab had 25 ACP and 32 ACP sample FMJ bullets, and Winchester brand factory load determinations could be made by the spherical stippling seen on the exposed lead bases of these samples, and "other maker" (usually Remington) was assumed for less characteristically-stippled bullet bases.

Someone with a more scientific background might be able to opine on what effect the dwell-duration of the heat from this high-pressure impulse striking and pushing against the bullet base might have.

[44man]

The heat applied to a boolits base is so short in duration that it can not melt the lead. A boolit too small for the bore can be cut on the sides from gas escaping past it. Pressure can leave powder impressions on the base but does not hurt a thing.

[Bucks Owin]

Glen Fryxell, cast bullet "guru" has a good analogy regarding gas pressures at work in an article of his about bullet lube. He likened gas pressure molecules to a swarm of tiny angry bees. 50,000 gas molecules will fit in an area .001" wide!

Sure don't need much of an "escape route" for those "bees" to do some cutting on the boolit base!

Dennis

[9.3X62AL]

Long Point--

The 10mm project with the RCBS 200 grain TC is about to commence shortly. The principal reason for the 200 grain boolit was--well.......the 180 grain boolit. In my M-1026, the 180 grainers needed to go at least 900 FPS, or the slide would "short stroke"--very weak ejection, and the slide would fail to lock back when the mag ran dry. If your boolits are meant for a 10mm as opposed to a 40 S&W, your 950-1000 FPS goal is near the floor in terms of the caliber's functional reliability. I started at ~6.0 grain of Unique with the 180, and finally got reliable functioning at about 6.4-6.5 grains.

I like the 200 grain boolit for the 10mm and hunting applications--potentially better penetration, 10% more weight going 1100 FPS--just barely sub-sonic, and about 93% of the caliber's full potential velocity-wise. I think 1250 FPS is possible with the 180 grain boolit in the 10mm--I just prefer the 200 grain boolit in the 10mm, the 180 does well in the 40. Unlike the 45 ACP, the 10mm does not take real kindly to down-loading very much. Not S&W 10mm's, at least--I've owned 2 of them to date, and they do better with more vigorous loadings.

[9.3X62AL]

I have a Lee 180 grain TC, and it has the miserable bevel base design element. I bought it for a now-departed Beretta 96, and I'm currently doing without a 40 S&W. At some point, I might grab one of the CZ-75 variants in that caliber. Of course, when you own a 10mm, a 40 Short & Weak becomes sort of superfluous.