Reloading 9mm with 357 bullets?

badguybuster · Oct 22, 2011

Ok, so I have been corresponding with a fella at Pinnacle Guns. Discussing having a 9mm cylinder made for my 627-5 (dont start with me fellas). I inquired about the .002 difference in bullet diameter and how that would affect accuracy. He told me it would mildly affect the accuracy but that I could reload the 9mm casings with 357 mag bullets? Have any of you done this? Also, wouldnt it be a little on the risky side of things? Imagine if you accidentally put one of those rounds in a dedicated 9mm barrel?

Rule3 · Oct 22, 2011

Why would you want to, and not just use 9mm bullets?

As to the conversion

sjmjax · Oct 22, 2011

Maybe not quite what you're looking for but I did experiment with 158 grain / .357 diameter bullets in 9mm cases.

My efforts were to shoot them in a 9mm subgun with a shot-out barrel. The bullets bulged the 9mm cases quite a bit. Didn't try them in a regular pistol barrel but they chambered in the generously chambered subgun barrel.

Ammo was remarkable accurate. The oversize lead bullets picked up the vestigal rifling and performed without leading. Fired cases were badly bulged. Probably from the high pressure and open bolt operation of the gun.

Eventually found proper replacement barrels and didn't pursue the matter further.

Not sure I'd recommend the practice in a regular 9mm semi-auto handgun. The revolver might handle it fine if the ammo chambers properly.

fredj338 · Oct 22, 2011

Well, I guess it depends on your accuracy requirements but shooting undersized bullets has never proven satisfactory fo rme concerning accuracy. An undersized bullet (0.355") in a larger bore (0.357") is going to "rattle" dwon the bore & not be properly stabilized as it leaves the bbl. Now loading 0.357" bullets in the 9mm may work fine, it will depend on the cyl fit of the slightly oversized round, but many 9mm guys shoot 0.357"-0.358" lead bullets in their semiautos w/ good results.

mtgianni · Oct 22, 2011

Have the throats sized to exceed the bbl diameter by 0.0005". Size your bullets accordingly and get a custom expander for your dies. If you are doing it just to fire cheaper surplus ammunition buy a 9.

Paul5388 · Oct 22, 2011

Here's the Lee 105 gr SWC (not WC) loaded in 9x19 brass that is shot in semi-autos of various makes. Walther P1s don't like it, but it'll even shoot decently out of a Makarov (.358" bore).

I size these at .359", but that is basically just lubing without sizing.

Calliope · Oct 23, 2011

If you think about the millions (not an exaggeration) of rounds of .311" russian ammo that went down the .308" groove barrels of Ruger Mini Thirties over the past few decades without trouble, a .357" bullet going down the.355" groove barrel of a 9mm is not going to cause much trouble.
During the ammo and component shortage back in '08 I shot .355" and .356" jacketed ammo in my .357 magnum with a .3585" groove diameter bore and had no issues with accuracy. I also shoot .356" jacketed bullets in all of my 9mm's without any pressure signs or changes in velocity.

Unless your 9mm load is right at the brink of blowing up a gun with .355" bullets, firing a .356" or .357" bullet is not a problem.

the only issue might be a problem with chambering a 9mm round with a .357" bullet if you have a tight chamber.

There is also a lot of data out there for all three bullet diameters in the .38 Super, and the data isn't watered down for the .356" or .357" jacketed bullets. Almost all modern Supers have a nominal .355" groove diameter.

There's a lot more tolerance for slight mis-matches in bullet and groove diameters than you might think.

TSQUARED · Oct 23, 2011

I do not have any experience loading 0.357" bullets in o.355" bores. Howver I did load some 124 gr Montana Gold JHP (0.355") and 147 gr. Star FMJ (0.355") for use in a S&W 627PC chambered in 357 Magnum. With the 0.355" bullets the groups at 50 ft were 1.5 to 2 in ches while a 130 gr. FMJ o.357" provided 3/4 to 1 inch groups.

SMSgt · Oct 23, 2011

I load 9mm Mak bullets (.363 dia) in 9mm Luger (.355) cases all day long (after trimming to 9x18 of course) for my CZ-82. The first loading looks odd but on firing the cases fireform to the 9x18 chamber. The issue will be if the larger diameter bullet will even fit into the smaller 9mm chamber. things may get a bit tight, possibly raising pressures dangerously. All in all, most multi-caliber conversions don't have as good accuracy (.22LR/.22 Mag for instance).

If you insist on shooting smaller calibers in larger caliber bores, just accept the loss of accuracy it produces. Otherwise, match the chambering to the bore.

kenjen · Oct 23, 2011

when i first shot my(new made in italy) beretta 92fs it leaded up real bad so i sluged the barrel and found it to be over sized, so i had penn bullets make me some 125grs. sized to .357, no leading and alot better accurcy.

David Sinko · Oct 24, 2011

If you have cylinder throats that are about .002" under groove diameter you might have a serious accuracy problem but I doubt you'll have a safety problem. I suspect that my first run 8 shot .38 Super revolver suffered from this problem but I never slugged the bore or cylinder throats to be absolutely certain. Rumor was that they had .355" cylinder throats and a .357" barrel. Mine was very accurate with plated and jacketed bullets but keyholed badly with all cast bullets of every diameter from .355" to .358". I tried some pretty heavy cast bullet loads and never experienced any symptoms of excessively high pressure. If you are pondering this conversion to be able to shoot 9mm jacketed ammo, it might work. I think it would be best to ensure that the cylinder throats are .001" over groove diameter. But then again, 9mm bullets out of .358" cylinder throats probably won't work too well either. I traded away that Super and refuse to own any revolver that behaves in a similar manner.

Dave Sinko

WilliamWaco · Oct 24, 2011

I have four modern 9mms. All 1911s of various makes. every one of them slugs .356.

I don't use .357 bullets in them because I consider them too heavy but I do use the same 0.357 diameter sizing die for both with excellent results.

Also for a pertinent discussion, see:

Hello, to the bullet Masters out there! Question... - Cast Boolits

M29since14 · Oct 24, 2011

I have seen lots of folks claim it a good idea to use bullets larger than .355" in some 9mm pistols, particularly the Beretta 92. I think this is driven by the idea that the bores of these barrels may be very slightly oversize. I have tried Hornady 125-gr XTP .357" bullets in my older Beretta 92F, and they did improve accuracy. Whether that was because of the size of the bullet, or the possibly higher quality of the bullet (compared to what I had been using), or a combination of both, I cannot say.

As to whether it is wise, I guess someone with the sophisticated equipment needed to do the testing could tell us a lot more, but in the case of my limited testing in my Beretta, everything seemed to proceed normally. The loads I tried were not really hot loads. I selected a single, moderate powder charge that I thought would be safe for all of the several bullets I was testing. I had used the charge and powder before and knew the combination tended to be accurate and function well in my gun. There was no sign of anything alarming - gun functioned normally, fired cases looked normal, accuracy improved.

You probably could have fired my loads in any 9x19 pistol without the slightest problem, regardless of actual bore size, but if you worry about this and feel like you have to keep the loads with .357 bullets separate, obviously the easiest thing to do is don't.

Pocketfisherman · Oct 25, 2011

Ruger makes a 357/9mm convertible single action with two cylinders, and there is a lot of discussion on this very topic on the ruger forums. The net is that it works well and improves the accuracy since the barrel bore is sized for 358 bullets. There are also some people who say they got good accuracy with 9mm as is, especially +P commercial loads in the convertible pistol. If you want to do it, go ahead as it will either work with regular 9mm bullets, or you can upsize if it does not. With two cylinders available, you'd have more bases covered if ammo shortages occur again in the future. Plus you can use cheap 9mm ammo to practice.

Maximumbob54 · Oct 25, 2011

Paul5388 said:
Here's the Lee 105 gr SWC (not WC) loaded in 9x19 brass that is shot in semi-autos of various makes. Walther P1s don't like it, but it'll even shoot decently out of a Makarov (.358" bore).

I size these at .359", but that is basically just lubing without sizing.

Oooooo...

I have that same mold, and have my own Mak dies now... I think I have an addition to my weekend plans now. I was holding off from buying the Lee Mak mold since it looks so unexciting. I will have to try this first. Thanks for the idea!!!

badguybuster · Dec 18, 2011

Yes, but the leads bullets heat up (if I am not mistaken) during the firing process and thereby are able to meld to the bore shape a little better than say a 357 mag Gold Dot would in a 9mm. Is this correct? I have no intention of actually doing this, I am just curious since I have heard of others actually doing it The fella in question, claims to have loaded a 180 grain XTP (357) in to 9mm at +P velocities. I will see if I can find the thread again.

Josh M. · Dec 19, 2011

mtgianni said:
Have the throats sized to exceed the bbl diameter by 0.005". Size your bullets accordingly and get a custom expander for your dies. If you are doing it just to fire cheaper surplus ammunition buy a 9.

I usually aim for throats to be 0.0005" larger than my groove, not 0.005"!

Paul5388 · Dec 19, 2011

Josh, that appears to have been a typo, but still good that you called attention to it.

SMSgt · Jan 8, 2012

The question is whether the .357-loaded 9x19 cases would fit the chamber or not.

VAdoublegunner · Jan 10, 2012

In this case I don't know, but it seems like it would work if the 9mm cylinder was throated properly for 357 bullets. Will the extra .002 allow them to properly headspace, or would the neck diameter be too tight? I guess it could be reamed as a bit of a "loose" chamber.

I do recall being at the range one time when the 357 Sig was new. The guy beside me was shooting a new gun and had pierced a primer or two, split a case neck or two, then bulged his brass pretty bad. He came over to ask me what was wrong. The obvious answers and advice didn't seem to impress him since he said he was only using the "starting load". When he went back to the bench to fire when the range went hot again, I picked up my stuff and moved down 4 places. Three shots later he blew a case big time and welded the gun shut...almost. Nice blown case was stuck fast in the ejection port. You guessed it...he was loading 357s instead of 9mm bullets and was going for max velocity, even at the "start" load. So apparently it doesn't always work out too well.

Reloading 9mm with 357 bullets?

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