Lee Loader

As the header says, how much do 38 special cases stretch when reloading at subsonic velocity and FL resizing?
Do they ever get so long that they fill a carbine 357 mag chamber?

I don't think a case can grow an 1/8" without blowing out first.

I have never known straight wall cases to grow enough to need trimming

I don't know about 38s but my 45 Colts at 35-40 cycles have gone from 1.285 down to 1.260 .

I've run loads from the bluper that bounced off a 25 yd backer to a 1200 fps 350 in a carbine and well into the Ruger only levels . Those 300 aren't used up yet but are very likely to become 45 S&W .

I use some of mine for close to ten years now. .38spl cases are built like tanks. Occasionally I have a split one, of one is stepped upon, but I never had one that was significantly lengthened. I even stopped measuring it years ago.

Only time I ever trim pistol brass are new ones for my 357 and 44 magnum nuclear loads so crimps are the same.

That's really good news, I have some winchester cases and also PPU, hopefully they won't stretch..

As a rule straight wall cases don't grow they get shorter . The ACP clans will eventually show the collapse of the extractor groove.

I had to trim some 45 Colt cases because they were too long according to SAAMI specs. That was the only time I have had to trim pistol brass. I've reloaded 38 Special cases for decades. None of them have ever given me any trouble.

My experience is just the opposite. I.e., my .357mag. brass grows shorter after several light - moderate loadings. Those then become .38Spl. brass after trimming to length of course.