Technical question on slides, for a change

[YVK]

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?

[TheNewbie]

I don’t know the answers here but this sounds like an interesting topic.

Did you measure any non 9mm guns?

[JCN]

@YVK did you know that by the breech face some slides are cut so thin… that they actually have holes to see brass like a loaded chamber indicator or even complete cut outs so the cartridges can be ejected out of them!

(am I misunderstanding something? The slides don’t see the pressure contained by the case and the barrel….)

[YVK]

No. I have only two non-9s, both described as mature designs in a neighboring thread. Didn't think they would help in understanding how modern designs are made.

[YVK]

(am I misunderstanding something? The slides don’t see the pressure contained by the case and the barrel….)

Not as much of a full explosion but sees enough pressure to be moved backwards and cycled in 0.05 sec. The ejection port side has, naturally, ejection port that will bleed off some pressure. I presuming (but not stating as a fact) that breech face and wall opposite the ejection port will see the most pressure load. We have certainly seen breech faces cracked.

So the question remains: why SIG makes their wall 0.17 thick while HK makes theirs 0.24, while taking an effort and cost to thin out that wall towards muzzle (P365 does that too but to a much lesser extent)?

[MattyD380]

Well, most of the explosive force would be contained within chamber/barrel walls… so it wouldn’t be putting much blast pressure directly on the slide walls. Which I guess is JCN’s point.

By the time the breechface separates from the chamber, most of the pressure would have already dropped, and blown out with the bullet. At least in a locked-breech gun.

Unless the chamber walls need the slide walls on the outside to resist the explosion. But it doesn’t seem like it would work like that? Then again, I got Cs in science.

Nevertheless, this is interesting. I feel like we need more “how guns work” threads.

[AdioSS]

As an owner of many Berettas, this thread is amusing.

[YVK]

Obviously, slide's wall thickness may have nothing to do with pressures generated during ignition. I simply found it interesting that, with the same caliber, wall thickness on full sized guns was 15%-35% beefier than on a slim gun.

[MattyD380]

Obviously, slide's wall thickness may have nothing to do with pressures generated during ignition. I simply found it interesting that, with the same caliber, wall thickness on full sized guns was 15%-35% beefier than on a slim gun.

Yeah, it’s a worthy question.

Maybe it has more to do with the mass/momentum/cycling speed of the slide, than strength/durability.

[zaitcev]

It would be very interesting to polish a little chunk of SIG and HK slides and look under a microscope.