[Blakenzy]

Can bullets cast for 9mm Luger (.356 diameter) be loaded in .38 Special cases? Or will the .002" difference ruin function and accuracy?

[Grumulkin]

They can be loaded in 38 Special cases. They will function just fine. Accuracy may improve, stay the same or get worse.

[loadedround]

Yes you can. However the smaller diameter bullet probably won't stabilze properly and also could cause gas cutting since the bullet does not seal the bore properly. This would lead to premature barrel wear in a fairly short time. However a Colt barrel would probably handle the smaller diameter bullet better than a S&W since the Colt has a slightly smaller bore diameter than the Smith. I have shot 9mm jacketed bullets in my Colt Python just to try it a few years ago. Accuracy was about fair at 15 yds . BTW, Ruger sells(sold?) a Blckhawk 357 Mag with a 9mm fitted cylinder for many years. I haven' checked to see if they're still a current production item. :)

[earplug]

Undersize lead bulllets lead up my revolvers. When the build up gets just right the bullets keyhole at fifty feet.

[Blakenzy]

You mean they keyhole because they group very tightly or that they tumble in flight striking sideways?

[Mal H]

They will tumble in flight and won't hit the target nose first.

The warnings about excessive leading are true. You want the bullet to fully seal against the grooves to prevent blow-by. A lot depends on your barrel, but that .002" might be enough to cause the leading.

In general, as you probably know, you want lead bullets to be a little oversized compared to their jacketed counterparts, not undersized.

You can probably push one of those bullets down the bore of your barrel quite easily with the proper dowel and then measure the actual bore size. You will also be able to see if the lands are deep enough to stabilize the bullet.