Question for reloaders

CBA Member

lotech posted this 25 January 2026

Yes, you can use them, And you're probably right - you won't get maximum accuracy, especially if the bullets are cast. However, if your bullets are jacketed, they may shoot pretty well. Jacketed are a lot more forgiving than cast when it comes to accuracy.

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CBA Member

beemer posted this 25 January 2026

I have a convertible 357 Blackhawk. I have not reloaded 9mm for it but have shot jacketed factory loads Accuracy is spotty but not terrible, did better with 124 grn. bullets. The long jump to the rifling doesn't help either.

If they are cast I would expect they will lead the bore. As already stated jacketed is more forgiving.

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Standard Member

tomme boy posted this 26 January 2026

Your barrel is 0.355" or should be so go ahead.

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Boschloper posted this 26 January 2026

I too have a convertible Blackhawk. In 9mm I use a Lyman round nose (don’t remember the number), powder coated and sized .356. It isn’t as accurate as the 358156 in 357, but is ok for casual plinking and doesn’t lead the bore.

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Standard Member

BJung posted this 26 January 2026

Yes you can. I PC my .355 bullets twice and when resizing, get .357". I never tested the loads for accuracy yet.

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CBA Member

Coydog posted this 26 January 2026

I use 9mm cast bullets in my 357 mag . Thy normally come out a little bigger from the mold and just size them to the gun I use them in .That is the the thing about cast you size them to fit the gun you use them for. Remember you go .001 or .002 over the size that the slug is .

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CBA Member

Aaron posted this 26 January 2026

Yes. For target shooting and general plinking (Cowboy Action too) I use both cast and jacketed 9mm bullets in my 38's and 357 revolvers. Cast bullets work the best and lately I have tried the Hunters Supply Slick Coat 9mm 124gr bullets which spec out at .356".

My cast bullets I size to .358 which is about what they are from the bullet molds. They just get kissed by the size die. Mind you though, I am not shooting any of them at magnum velocities. For the true magnum loads, I use bullets of appropriate hardness, weight, and alloy for that purpose. I do NOT shoot jacketed "9mm" bullets of .355" in my 357 Mag at magnum velocities. At 700-900fps, no worries.

With rifle in hand, I confidently go forth into the darkness.

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Standard Member

TRKakaCatWhisperer posted this 26 January 2026

Can I use 9mm (3555) bullets in a 357 chamber? I'm not looking for maximum accuracy as I am just plinking. I have boxes of 3555) bullets.

Roger Ulrich

Yes and no. I use the conical 9mm cast bullets in several .38 and .357 pistols. For some it is THE most accurate, others not. But the work.

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CBA Regional Director

Tom Acheson posted this 27 January 2026

Reminds me of a long ago expression of terminology. It was said you are either a reloader or a handliader,

A “reloader” is someone who buys components, adheres to loading manuals and assembles rounds.

A “handliader” is someone who carefully reviews loading manuals but makes minor adjustments to powder quantity, how brass is prepared, primer selection, OAL ctg. length and few other details.

My guess is that this forum is populated mostly by handloaders.

FWIW

Tom

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MP1886 posted this 27 January 2026

One will find out if they slug their barrels that most 357 magnums run a 9mm bore/groove. As for the Ruger 357mag/9mm convertibles more than likely the inaccuracy of the 9mm is due to the large cylinder throats. Check your cyclinder throat diameter. If it anything over .355 it isn't going to help accuracy. As for the long bullet travel, that's not so, unless, again, the throat is large. Many of us have the Ruger 45Colts with the 45acp cylinders and all claim, including myself, the finest accuracy ever seen. the 45 acp cylinder has a pretty tight cylinder throat.

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Boschloper posted this 28 January 2026

+1 to the above comment by MP1886. My .45 Blackhawk convertible with the auto cylinder is most likely the most accurate handgun I own. Way more accurate than my .357 Blackhawk convertible with the 9mm cylinder.

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CBA Member

beemer posted this 28 January 2026

All of the cylinder throats of my Blackhawk are .359. I need to slug the bore, been tinkering with it lately but haven't done it yet. I can see that would be a problem. Could it also be also why the longer 124 grain bullet shot better ?

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Standard Member

MP1886 posted this 28 January 2026

All of the cylinder throats of my Blackhawk are .359. I need to slug the bore, been tinkering with it lately but haven't done it yet. I can see that would be a problem. Could it also be also why the longer 124 grain bullet shot better ?

I presure that is the throat measurement on the 357 magnum cylinder? If so it would be better if it were closer to .358. If that's on the 9 mm cylinder it is entirely too larger.

You all know that if you shoot cast bullets you can load and shoot the fattest cast bullet that will let the cartridge chamber easily and that will not hurt anything and your accuracy may improve.

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Premod70 posted this 28 January 2026

If you're going to spend the time to reload why not set the revolver up to the proper specs for any bullet you choose. That being a cylinder throated to a consistent inter diameter and a bullet large enough to seal properly.

Dale Flinchum

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CBA Member

beemer posted this 28 January 2026

I measured the Blackhawk today. The 357 cylinder throats are .359, the 9mm cylinder is .358. I used pin gages to check them. All the throats seem to be consistent. I drove a slug through the bore and it is .3572. The 9mm sounds large but considering the bore is a little over .357 it might be best.

I recently lapped out a Lee .358 push through sizer to .359. You can feel the bullets go through the throat pushing them by hand. Shot some powder coated bullets in the Blackhawk with good results,50 rounds and a nice shiny bore.

I think I will play with the 9mm cylinder when I take this back up, in the middle of shotgun stuff now.

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Standard Member

MP1886 posted this 28 January 2026

I measured the Blackhawk today. The 357 cylinder throats are .359, the 9mm cylinder is .358. I used pin gages to check them. All the throats seem to be consistent. I drove a slug through the bore and it is .3572. The 9mm sounds large but considering the bore is a little over .357 it might be best.

I recently lapped out a Lee .358 push through sizer to .359. You can feel the bullets go through the throat pushing them by hand. Shot some powder coated bullets in the Blackhawk with good results,50 rounds and a nice shiny bore.

I think I will play with the 9mm cylinder when I take this back up, in the middle of shotgun stuff now.

Let me give you an idea. I have a 9mm P08 Luger. The barrel interior is very nice except the groove is .359. Okay I have a swage for revolver/pistol size bullets. One of my dies happens to be .359 for the swage. So I will take 35 caliber cast bullet that would be compadible with the 9mm pistols I own. I will make a nose portion of the swage punch to duplicate the nose on the cast bullets I want to use. First I size and lube the cast bullets. Remember they are not as fat as the .359 diameter I need. The reason I lube them before swaging them up is so I don't lose the lube grooves. I swaged them up and I couldn't believe how accurate that fat groove Luger shot. Yes the loaded cartridges with the .359 bullets easily fit in the chamber.