Loading 9mm bullets in 38 special

NoirFan said:

. Am I right in assuming that the slightly undersize 9mm bullet will generate less pressure, therefore requiring a slightly higher powder charge?

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I'm not sure that's the right way to think about it. I'm also not confident that a mid-slow powder like HS-6 is a great choice for this experiment (though H110 would likely be far worse). I don't know that the combination of an undersized bullet with no ability to apply a firm roll crimp is going to let you generate the pressures needed to get good results from HS-6. (HS-6 isn't often thought of as a great 38 special powder, except maybe for +P loads.) I don't think stuffing an overcharge of the wrong powder into the case is a great solution.

Stepping back further, some people manage to get OK accuracy out of undersized soft bullets by "bumping up" the diameter with a quick jolt of pressure from a fast powder. FMJ's are not a soft bullet. They are unlikely to "bump up" no matter what you do. I have seen .001 undersized FMJ's/JHP's fired out of USPSA/IPSC open guns (which are generally running very high pressures over large charges of mid-slow powders, including HS-6) keyhole terribly. When I say "terribly," I mean: unable to stay on a cardboard USPSA target at 15 yards, and unable to reliably hold the A-zone at 7. The bullets don't obdurate to the bore, and they don't engage the rifling. Bullets just rattle down the barrel and come out any which way.

Will that happen for you? No way to know for sure but to try it, but I would have low expectations of being able to make your revolver throw anything but knuckleballs with those bullets.

After heeding ATLDave's advise I think I would also slug the barrel/chamber throats and measure the "9mm" bullets to see how much difference you're dealing with (.356" bullet vs ,357" groove dia.?). I would taper crimp the bullets since they have no cannalure and use light, starting loads...

Maybe. I might start by seeing what happens if I simply drop a bullet through the throats of the cylinders and then through the bore. Might give you a sense of how much mismatch you're dealing with and if you have any prayer of getting the rifling to engage the bullet.

Please post your results. I am interested in this whole experiment, though it's not one I would bother with myself!

HP-38/W231 is a far better choice than HS-6 for this application. One question, if you were looking to build inexpensive plinking .38 Special ammo why didn't you just but Lead bullets and load them instead?

NoirFan said:

I've got HS6 and H110 on hand, and from flipping through my manuals it seems like HS-6 is the right way to go.

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I have no experience with HS6, but if it would be applicable with a 125gr. .357" bullet it will work essentially as well with a .355" one. Obviously H110 would only be applicable to true magnum loads. In creating lesser loads there are probably better choices than HS6, but I'm not familiar with its properties. I use Titegroup in my 38 special; many use HP38.

NoirFan said:

The closest load data in Lyman #50 is for the 125gr JHP, showing a spread of 5.6 to 7.4 grains. Am I right in assuming that the slightly undersize 9mm bullet will generate less pressure, therefore requiring a slightly higher powder charge?

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Yes, the undersized bullet will produce a lesser degree of bore sealing and more chamber pressure will escape past the bullet, lowering the pressure curve directly (including its peak). A slightly heavier charge may be required to reach desired pressure and velocity.

NoirFan said:

Also I usually use a mag primer with HS6, am I OK to do so here?

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Again, no HS6 experience, but I don't see the sizing of the projectile as affecting this consideration.

NoirFan said:

For seating and crimping: there is a faint crimp groove on these bullets from their past lives as 9mm loads. I'm just going to seat to this depth and put a slight roll crimp into this groove. Any potential issue with that?

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I would probably mimic the seating depth my load data uses, but it's probably not critical. I would only consider a roll crimp if these are pretty violent loads, a light to medium taper crimp should suffice for most and will reduce the chances of piercing the plating and starting it to shed.

Using a .355" plated or jacketed bullet in a nominally .357" gun isn't the end of the world. When you shoot 9mm in a Blackhawk convertible you are doing just that. The reputation for accuracy isn't great, but with some load development I suspect at least decent results are possible.

I would limit your 9mm bullets in 38 Special to about 2.5-2.7g Red Dot/Clays/Titewad/AA#2/Trail Boss or any other really light charge of uber fast powder. It will get the bullet out the barrel, make a noise for you and be of low enough recoil as to not pull the bullets out of the case and lock up the cylinder. You should check your remaining chambered cartridges after shooting 3-4 shots to see if the bullets are staying in place. For a similar low recoil load using a slower powder (even like Unique) will produce lots of smoke and powder flakes flying around.

If you see keyholing or really innacurate shots, the bullets may not be engaging the rifling.

When I load 9mm FMJ bullets in .357 I don't expand the cases at all, I just seat them deep and crimp on the nose. Then I use data for a heavier bullet to compensate for deep seating the bullet. Agree HP-38 is the better powder choice.

NoirFan said:

BTW, thanks for your past posts on HS6. They informed development of my own standard 38 +p practice load with 158gr SWCHPs: heavy charge HS6, mag primer, heavy crimp.

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You're welcome. I'm glad you found my posts useful. We all should share our work because that's what makes our community stronger and better.

In the near future I'm going to be testing W572 in several cartridges, the .38 Special +P will probably be first. I'm hoping to get as good a results with it as HS-6 and I will post my data for discussion and for others to verify.

If your just having fun and messing around. Try setting them on a steel surface and whack the tips with a hammer. They might bump up to .357/358. Paper patch is another option.

The only really good solution is to buy a 9mm pistol.

I have been known to buy a gun for no better reason than having a partial box of ammo on the shelf.

Hey, if it doesn't work, let me know what you would take for the left overs shipped. Good luck with the experiment.

I think they will shoot plinker level well enough to entertain unless you have a fat bore revolver.

I have put quite a few skinny jacketed bullets through my sp101. Never shot great, but worked fine for 10 yards and in. I used a fast powder. Titewad, red dot, 231, american select, titegroup etc. I used load data for the similar weight of .357 bullet. I was no where near full power mind you. Velocity was 800 FPS give or take a bit with 115 class bullets, a bit slower with the real fast powders.

I used a light crimp. Nothing more was necessary for me since I was loading light. You could try using a 9mm expander in your sizer if you need more neck tension on the brass.

The Ruger 357 convertible shoots factory ammo 9 and 357 with no problems. Different chambers. The barrel handles both jacketed bullet diameters. No lead or soft bullets.

Only problem i see reloading , is getting enought neck tension . A mag primer is needed with HS-6. Firing of the primer may move the bullet to soon.

On seating the bullets, the case neck area needs to expand a minimum of .002" for good neck tension.

Do not over crimp.

HS-6 leaves some residue that can get trapped between the ejector star/cylinder when ejecting fired shells. Point muzzle up when ejecting.

I've shot some 115 grain fmj .355 bullets i got for free through a 686 before. Don't remember the load but was a mild 38 special cause there is no way I would have pushed them hard.
Turned out they shot pretty good.

One reason for shooting them soft was to help them spin in the rifling vs stripping the rifling from being pushed hard and undersized.

Bore size is all over the place when comparing guns made by different manufacturers, and even the same manufacturers from lot to lot. Don’t assume that your .355 bullet is traveling down a .357 tube because in actuality a lot of revolvers truthfully have 9mm bores. They are really close so it works well enough that people don’t know any difference. Load them to the levels of standard 38spl.

Full Metal Jacketed .355" bullets should grip the lands well, because of the thick jackets. Don't know about plated? Lead is a no go, for sure. Really all depends on the groove diameter of the barrel.

Years ago I loaded up some .355's in 357 Mag cases and while they shot just fine, they didn't have much in the way of seating tension and depending on the brand of cases used some went in with barely any effort at all. As it was just an experiment I didn't pursue a remedy...but loading without flaring/expanding as PO2Hammer suggested sounds like a good way to allow for the smaller diameter.

NoirFan wrote:
...9mm 124gr FMJ from American Reloading...

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Are you sure those are Full Metal Jacket bullets? Looking at the bullets shown in the picture, they appear to be copper plated lead bullets (also known as Full Metal Case or Total Metal Case) bullets. If so, they generally use load data for cast lead bullets rather than jacketed bullets.

Over the years I have had quite a few 38/357’s. I have slugged the barrels of each and none of them had a grove diameter greater than .355. I did have a 9mm HK that slugged out at .358. Because of this, I have often used 9mm bullets in reloading 38’s with no ill effects.

I could not get adequate bullet pull for 9mm bullets in .38 special, even with no expander plug.
C.E. Harris wrote about in in American Rifleman. He couldn't, either; so he had a tight neck sizing die made up.
He said they did ok after that, the little difference in bullet vs groove diameter did not matter as much as you might think.
He said 9mm bullets did not work in .357 Magnum, they actually broke up.