I speculate that the ‘don’t use .38 in a .357’ idea came from the fact that manufacturers of the absolute cheapest ones will cut any corner they can if it’ll shave even 10 bucks from the manufacturing cost. Slightly cheaper steel will save a few bucks, but could be subject to erosion of the metal when using 38, causing problems using 357 later. The manufacturer would therefore recommend against using 38, and explain why. Some people saw that, and generalized it to all 357s, rather than just the cheapest. Just my WAG on where the idea originated.
.38 Colt (short) and .38 Long Colt as well can be used in a .38 Special but not always .38 S&Ws ------ they are a hair thicker.
Grandpap was a big fan of .38 Colts in his pistol for dispatching assorted animals around the farm. Tons less noise or through-and-throughs.
It’s 100% safe and appropriate to fire .38 special out of .357 magnum. I’ve done it a million times. That whole thing about lead buildup is bunk.
The only problem I’ve ever seen from firing .38 special cartridges from a .357 revolver is that not every magnum revolver will shoot the .38’s accurately. Many, if not most, revolvers handle them fine. There are a few, though, that will shoot .357’s just fine, but throw .38 specials all over the paper. This varies by individual gun, rather than model, so the only way to find out with your particular gun is to try both.
With every .38 I’ve had it wouldn’t have even been possible to close the action with a .357 cartridge in it.
With full wadcutters possibly? Been too long since I had a .357 to remember for sure. Seems I did have something as a fallback to +P rounds.
Depending on the OAL of the loaded cartridge, it can be done. It’s easier on low end revolvers where the chambers aren’t bored to spec.
I’m trying to remember which movie it was (for some reason I think it was a Matt Helm movie) where somehow in the course of the movie a gun gets loaded with a completely wrong caliber bullet (tiny bullet in a big rifle, or something). I forget why, I think they were down to one bullet and it was the wrong one. Much later, the traitorous bad guy picks up the gun and shoots our hero. Bullet bounces off the good guy’s chest; both stare at the slug on the ground.
How realistic is this? I’m not sure I’d want to stand in front of a bullet being fired, even if there was no barrel to speak of (or an outlandishly large one). It’s still got to pack a whallop and likely penetrate skin a bit?
A small bullet being fired out of a larger bore arm might flop around inside the barrel or something. The rifling in the barrel certainly wouldn’t catch so the smaller round wouldn’t have any spin to it. Between that and the erratic movement through the barrel velocity would be greatly affected.
I still wouldn’t stand in front of it.
One time I was at the qualification range and somehow a .40 S&W round got mixed in with some 9mm Parabellum ammo. Someone accidentally loaded it in in their 9mm pistol. It really screwed up their pistol when they fired it!
Yes, I shudder to think what a mess a tumbling bullet might make in a barrel…
??? That is a full mm oversize! No way that would possibly chamber enough to fire. It might go in the magazine and then get jammed in the mouth of the chamber, especially a Glock, which has a fairly significant “funnel” at the mouth of the chamber. (the cause of the “Glock bulge” on fired brass)
All modern pistols have some feature that prevents the gun from firing out of battery (slide and barrel not fully locked together) so the gun won’t fire if the oversized cartridge didn’t chamber fully, which would take hundreds of pounds of force to do.
This was about 8 years ago. All I remember is the cartridge was ignited and the casing split inside messing up the sear, the ramp, the extractor, and so on. I as not on the hot line at the time, I was in the reloading booth. They couldn’t even get the slide to open up and and to secure it and take it to a gun smith.
I’m fairly certain it was a 40 in a 9 and not the other way around. But like I said it was about 8 years ago and it didn’t happen to me.
You are right and wrong.
38 special in a 357 is perfectly safe and effective and done all the time - any revolver that can chamber a 357 mag is perfectly safe to use 38 special rounds in - the 38 Special is just a SHORTER (and less powerful) round so it shoots perfectly.
It is impossible (without breaking the action of a revolver to shoot a 357 mag in a 38 special because it is too long - the revolver would not rotate it into the chamber - it would be physically obsructed from doing so by the length of the shell.
You are right that a rimless 380 will not work in a 38spl revolver - rimless being the problem. I suppose if you were a gunsmith and modified it to use moon clips with the 380 shell you could make it work though that would take specialized skill and tools - though an intersting oddball if you could get it done 
Been done as I noted upthread some time ago.