Technical question on slides, for a change

[jh9]

HK likely makes theirs visibly overbuilt in that area because HK.
That's my conclusion.

Your P30 is still largely based on the USP that was designed 30 years ago, isn't it? Unlike the VPs, the .40s weigh the same as the 9. So either way I assume they were .40s first and foremost (or at least designed to accommodate the .40) which is probably part of the reason why they're thicker.

I wonder how an analogy to the F-117 and F-22 works. The former being a product of the limited modeling ability of computers available at the time.

The 365 is probably closer to what a modern 9mm "should" be in terms of shedding extraneous weight. Without commenting on shootability... just function and lifespan. Another few decades of more data and better modeling will usually produce a more streamlined design.

[balance]

My guesses to this would be reliability, durability, and maybe even safety.

Reliability because with more mass the slide should slow down and allow everything to move into place even if, say, the mag springs have fatigued, durability because there's more metal there, and safety because the last pistol I'd want to have a KB with is with a pocket pistol chambered in a cartridge that was originally designed around a full-sized pistol.

[JCN]

My guesses to this would be reliability, durability, and maybe even safety.

Reliability because with more mass the slide should slow down and allow everything to move into place even if, say, the mag springs have fatigued, durability because there's more metal there, and safety because the last pistol I'd want to have a KB with is with a pocket pistol chambered in a cartridge that was originally designed around a full-sized pistol.

Regarding KB, it seems like most modern pistols are meant to blow mag down and extractor out as sacrificial parts.

So unlikely that the slide would blow out, the pressure just isn’t contained and held there to rupture the metal of the slide even if thin.

I am more concerned about barrel and chamber thickness of some of the paper thin 380s when shooting over pressure rounds. The LCP has had a history of barrel rupture when subjected to high diet of hot rounds.

[fixer]

I got induced into thinking about quality of steel that goes into making modern pistols. Following that, I took a micrometer and measured side wall thickness on several pistols. I presumed that most of "pressure load" happens around breech face so I measured a wall opposite the ejection port.
Four different full sized guns measured at 0.20+, with HK P30 being thickest at 0.24 (I again admired how intricate P30's design was).
SIG P365 measured notably thinner, at 0.17.

Obvious question is why is that? What allows slimline gun be made with a thinner slide, or are full sized guns way overbuilt, or what else is a factor?

I've done component design before for an automotive oem so here is my take...

There is probably a minimum thickness needed for high cycle fatigue. I think the entire discussion is due to a level of safety factor in design on top of double stack vs single stack dimensions.

This area you are looking at is loaded in tension mostly. However the vibration from the ignition/explosion likely contributes to some overall stress in the area. It'd be good to know if an ignition puts the slide near its mechanical natural frequency because this would drive further stress analysis...

With a full size pistol, double stack, there is likely also an assumption that the pistol will get dropped on this particular side wall area, etc. So the assumption is that the thickness should accommodate for some cracking and still maintain integrity.

With slim guns the safety factor here is much less but still workable.

So its like this generically

Double stack gun. Width will be around 1.0 inch. Slide internals need to be 0.6 inch. That leaves .2 inch per side for the sidewall area.
This area can have a calculated max stress, yield point, and fatigue point determined with modeling software and inputs.
Then a crack is simulated, and same stress analysis is done. 0.2 inch good? yep...ok...
No good? ok...what mass or dimensions are sufficient? 0.25. ok...drawing board time...need to get overall stress lower in this area so that 0.2 inches will pass our standards.

Single stack gun will have similar considerations but the safety factor in the model will be substantially smaller than a double stack gun.

[fixer]

Regarding KB, it seems like most modern pistols are meant to blow mag down and extractor out as sacrificial parts.

So unlikely that the slide would blow out, the pressure just isn’t contained and held there to rupture the metal of the slide even if thin.

I am more concerned about barrel and chamber thickness of some of the paper thin 380s when shooting over pressure rounds. The LCP has had a history of barrel rupture when subjected to high diet of hot rounds.

Ernest mentions a safety design feature of the 92 at about 20 seconds I thought was interesting and relevant here.

https://www.youtube.com/watch?v=Db8t-f54Im0&t=310s