What's the BIG difference .38 / .357 ?

[ToeRag]

I'm new to firearms.

I have a SW686 which will fire both .38special & .357

if you look at the cartridges they are almost the same! the .357 has a longer shell/cartridge but beyond that it's hard to tell them apart. Except of course if you fire them. WOW, what a difference.

So if I mic each with a digital caliper they are the same, around .380 give or take. So where does the .357 come in?

I assume there is a big difference in the amount of powder that is added to each round, and perhaps the bullet --- but what makes it such a huge difference?

 

[PotatoJudge]

You've got it about right, the case length is greater with the 357. Both 38 and 357 bullets are .357 in diameter. The 38 comes in as a historical leftover from when bullet lube was over-caliber and measured .380 or so.

There are some bullets and powders that are more suitable for one cartridge or the other, but mostly components are interchangeable with the 357 taking a heavier charge of powder.

 

[ReloaderFred]

The pressures the two rounds are loaded to are the biggest difference. The .38 Special is loaded to roughly 16,500 Copper Units of Pressure, and the .357 Magnum is loaded to roughly 41,000 CUP, give or take a few.

The .357 Magnum case is .135" longer than the .38 Special case. This was done from the beginning to keep people from chambering the higher pressure round in guns that were chambered for the lower pressure .38 Special, which were in common use in 1935, when the magnum round was first produced.

Both rounds use bullets that are nominally .357" in diameter.

The .38 Special was first a black powder round, hence the long case. If it had been developed as a smokeless round, the case would have been much shorter in length.

Hope this helps.

Fred

 

[fireflyfather]

Two other issues come up if you use .38 special rounds in the .357 gun, or if you reload your cases.

First: Using non-jacketed lead bullets from .38 special cases CAN leave lead buildup in the six chambers of the cylinder, making it harder/remotely dangerous to load full length magnum cartridges. The lead buildup prevents insertion of the cartridge, or it pinches the end, thus raising pressures in the gun. I've never personally had a problem with this, but it has been documented. It's not a problem if you only shoot magnum, or only shoot 38 special. Only if you shoot lots of .38 special lead rounds, then follow with magnum cartridges (and probably not even then).

Second: Because of the much higher pressures involved with the magnum, the cases tend to stretch a bit, just like bottleneck rifle cases. They need to be trimmed to prevent bullet pinching if you plan to reload them, and depending on how hot you load them, they can wear out fairly quickly. For this reason, it's easy to find once-fired .38 special for reloading. The .357 brass is generally kept by the owner as it's a known quantity, and nobody wants to buy four or five-times fired magnum brass. That means there is less of it on the market. This generally is never a problem with the lower pressure 38 special rounds. Some people reload that brass until it starts to crack.

 

[Grump]

The earliest cawtrigz wuz loaded with heel-based lead bullets, outside lubed and like a .22 LR, so a .38 bullet went into a case that was about .38 outside diameter.

Not sure how that fits in with .36-caliber percussion revolvers...

Moving the driving band of the bullet inside the case was called "inside lubricated" or something similar all the way up to the 1920s or '30s--I've seen the old boxes. Bullet diameter went down to .357 with the introduction of the .38 Special, a hot-loaded blackpowder improvement over the ones described below. THAT resulted in a lot of spare room in the case when it was switched to smokeless.

Somewhere in the middle was the .38 of various Colt/Smith & Wesson and long and short and such designations. The two makers put their names on cartridges that were pretty much identical for a while.