View Full Version : Can I mix 38 spc, 357 magnum, 9mm bullets?

February 1, 2012, 08:25 PM
38 special and 357 magnum's have specified diameters of .355" to .357".
9mm is specified as .355". Most of the bullets I've measured are +- 1/1000 which tells me they are really all the same bullet; all within manufacturing tolerance limits.

The Big Question.
Can I use 38 spc, 357 magnum, and 9mm bullets interchangeably when reloading as long as the specified height of the finished cartridge are in tolerance for the reload caliber I'm reloading?

February 1, 2012, 08:32 PM
As you note:
38 Special & 357Mag are the same diameter ... 0.357
9mm is slightly smaller ... 0.355

You could use 9mm in 38Special/357 weapons (accuracy might suffer a bit),
but I advise AGAINST the other way`round

February 1, 2012, 08:45 PM
Your theory is correct. Lower specified diameter bullet OK, but accuracy will suffer since it bounces down the barrel. Higher diameter bullet not OK. But I'm measuring a variety 9mm bullets between .354 and .356. And I'm seeing 38 spc between .356 and .357 (rarely higher, sometimes lower...). Is 1/1000 that important to a bullet searing it's way down the barrel?

February 1, 2012, 09:15 PM
Is [a coupla]/1000 that important to a bullet searing it's way down the barrel?

If lead, likely not.
If jacketed...

Misssissippi Dave
February 1, 2012, 09:17 PM
If you notice the rifling in the barrel you will see there are lands and groves. It is different with a polygonal barrel. The gas produced when the powder is ignited is what pushes the bullet out the barrel. When you have a gap between the bullet and the groove, gasses will blow by the bullet and excape before the bullet reaches the end of the barrel. If you are shooting lead bullets then those very hot gasses will also start melting the lead of the bullet. and increase the gas loss behind the bullet. You also tend to get leading of the barrel too as the liquid lead cools. Another problem is you have to increase the crimp a lot to secure the bullet in the case. Now if you slugged the barrel and found it to be on the tight side you might be alright with the 9 mm bullet in the .38 special and .357 gun. Generally speaking I wouldn't recommend loading 9 mm bullets in .38 and .357 cases.

I did try this a long long time ago and the results showed me I wasted some fmj 9 mm bullets. When I was loading .38 and .357 I bought wadcutter and semi wadcutter lead bullets that were supposed to be .358" and then resized them to .357. That gave me pretty accurate rounds. I was using a single stage press and weighed each and every round to ensure the charge would be the same for every load. The results of doing this gave me very accurate ammo. I even weighed the bullets to make them all 158 grains. That was when I had more then enough time on my hands for loading. These days I prefer a progressive press and just load mostly 9 mm range ammo. I can't see well enough any more where I need to have match grade ammo these days. Now I just shoot 7 to 10 yards out and occasionally 25 yards just to see if I can keep them all in center of mass at that distance.

February 2, 2012, 10:25 AM
I have successfully fired 9mm FMJ bullets in a .357 Magnum revolver, getting surprisingly good accuracy at 25 yards. The key was that they were high pressure loads, which caused the bullets to "slug-up" to the .358" diameter cylinder throats before they were engravd into the rifling in my .357" bore.

Trying to do the same thing with 9mm bullets at .38 Special pressures is not likely to be so successful, since the SAAMI max pressure is not likely to cause FMJ bullets to "slug-up" in that cartridge.

As for putting .357" diameter bullets down a .355" 9mm barrel, that is likely to increase peak pressure above the load data, but I don't know by what amount.


February 2, 2012, 12:34 PM
I had a Blackhawk with both .357 & 9mm cylinders. The 9mm were not accurate enough to bother with in that gun. I traded it for a model 19.

February 2, 2012, 01:51 PM
I use .356" jacketed bullets (Hornady HAP) in 9mm, no problems. But I wouldn't use .357" jacketed in 9mm, there's no reason to.

.356" plated bullets shoot well out of my .357 revolver with a .358" groove barrel.

February 2, 2012, 04:56 PM
To add to the confusion, I have used .357 lead bullets in a 9mm, with very good accuracy and no problems.
.356 diameter lead bullets sometimes tumbled, hence the switch to .357.
There will probably be a slight variation in diameters in a large box of bullets, just due to the manufacturing and sizing processes.

10 acre woods
February 2, 2012, 06:04 PM
I too was wondering the same thing on the 9mm side. Many days of research say that in a situation where you slug your 9mm barrel and find that you have a diameter of .356 then using a .357 lead bullet would improve accuracy and reduce leading. Some say that having a bullet sized 2/1000ths bigger then the barrel would be idea but nothing more bigger then that, some say 1/1000ths ideal. I didn't bother to research what would be ideal if the bullet was jacketed. Am I correct in this thinking or is this a bad idea.

February 3, 2012, 10:15 AM
Here is my experience on bore size vs bullet size.

One of my 9mm barrels slugs at .355, another slugs at .359 and the replacement barrel I bought for the same gun slugs at .355. My Dan Wesson revolver has 4 barrels, all which at either .356 or .357. My old Ruger P90 slugged at .450 and so does my 1911.

I size all my lead bullets to either .358 or .451. Most molds cast a bit over what they are supposed to because not everyone uses the same mix of lead and you can always size down. I've shot some over diameter bullets just to see what would happen (like .456 or .362) and nothing out of the ordinary came of it. I also have shot hundreds of .357 jacketed bullets out of my 9mm's with the same result.

So what does this say? Not all barrels are exactly what they are supposed to be, some are a little small and some are a little large. With lead bullets if it fits it the chamber don't worry about shooting it. With jacketed I never had a problem either, at max load, .002 over. I bought my Ruger P90 before I even had a clue about bore size and shot factory ammo that was .001 over for years. I've also shot plenty of plated bullets that were .002 over through it as well. Same goes for my 1911.