Small pistol magnum primers in .38 SPL?

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I have the opportunity to buy a large...like 10 years worth for me...supply of CCI and Fed SPM primers from the estate of a fellow shooter who has passed. The price is very low, like early 1990's low, so very tempting. I knew the guy, he was a serious reloader and bullseye shooter, and they were no doubt well stored and judging by the packaging they are not very old, so not concerned about condition. 16+ pounds of HP-38 and a couple odd 1 pounders to experiment with also come with the deal.

Problem is... probably not a problem, but just looking for opinions...I shoot very little .357 Mag. I'm shooting in .357 handguns and rifles exclusively, no .38s in the stable, but almost all of my brass (a lot) is .38 spl police brass. My standard target load is 4.5 HP-38 under the ACME 125 TC in .38SPL brass. Can spm primers be substituted with the probable reduction of a couple tenths of powder? Would I even need to reduce the charge?
 
Your standard target load is below maximum for the standard pressure .38 spl. A magnum primer is highly unlikely to increase your pressure to even the top of .38 spl standard level. Personally I would use the magnum primers in place of your standard primers using the same powder charge level without any worry of pressure problems. As with any component change it may change the velocity or accuracy a bit.
 
Totally Safe and a great idea!

Start recording new load data, starting low, and note the primers used. You should get a few more FPS with magnums but if you work the loads up there's no reason it won't be safe. Don't just use the same loads with the magnum primers though, make sure you specify in your data which primers you're using a generate new magnum primer data.
 
It should be no issue at all. you may have to adjust your load for Optimum accuracy a little bit but there is no danger as long as you're not already at Max
 
The cavernous 38Spcl case is mostly empty space when loading with modern powders. So it might even help !

I have verified over a chrono what the guys have told you above. No difference for target or plinking loads.
 
mag primer over standard primer question comes up a lots. i use mag primers in all my pistol loads,, 9mm, 40 s&w, 38sp, 357 mag, 44 mag, 45 acp. i have tested the different between the two with the same load. my 357 mag load the different is 20 fps between the mag primer over the standard primer.
 
I have been trying to shoot up a 1000 count brick of CCI #550 SPM primers that I bought during the lean years. I just loaded up some 45 acp today. Three loads in Speer small pistol primer cases. They were 4.8-- 5.0-- and 5.2 grains of Win 231, with Berry's and Everglades 230 grain plated bullets at 1.230 OAL. I had sold my M&P 45 compact last year, and am working up loads for my 1911 Remington 45 Carry pistol with the 5 inch barrel. My M&P loved Berry's 185 Round Nose Hollow Based bullets, the 1911 hates them. So I am back to the reliable 230 RN plated. It depends what reloading book you look at where the MAX loading is. But my 5.2 grains is not at the very top of most of the reloading handbooks.
 
I only use mag primers. All calibers, all loading. Main reason being that I mainly load for magnums and it simplifies my life. Never had an issue.
 
I've had issues with hard CCI standard primers in striker fired guns.

All my striker fired guns get soft Federal primers now for that reason.
 
I've had issues with hard CCI standard primers in striker fired guns.

All my striker fired guns get soft Federal primers now for that reason.

Interesting, I fed my striker fired XD a steady diet of small rifle primers for two seasons and never had ignition issues. My competition S&W revolvers got nothing but Federal but my striker fired ate anything and everything.
 
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I pretty much have shifted my usage to small rifle primers for everything but one pistol that will not reliably set them off. I just worked up my loads again for the substitution. You should have no problems but I would drop back a bit and work up againjust to be safe. Sorry about your friend though. I would jump on the deal.
 
Federal primers are highly favored by cowboy action shooters. We tend towards tuned guns with lighter springs and Federal primers are very reliable. The most popular chambering in the game is .38 Special which of course takes a small pistol primer.

A couple of years ago Federal standard SPs became scarce so many of us switched to the Magnum version. As others have commented there may be a bit of extra velocity but our cowboy loads are not close to Max so there's plenty of margin.

We found some unexpected benefits to the Magnum primers. The ammo seems less sensitive to cold temps. My friend who shoots black powder cartridges reports more consistent ignition. A recent article penned by a respected cowboy shooter showed that Magnum primers made the ammo less position sensitive (small charges of fast burning powder).
 
I shot a bunch of magnum primers in 9mm during Obamascare I when you could find nothing else. No issues for my low to midrange loads.

Same deal here, saw no difference, 38sp too...
Funny thing though, a few months later I mentioned this to the guy where I bought the primers and he said he would not have sold them to me if he knew I wasn't going to use them for magnums. :rofl:
:D
 
So.....follow up question....the Step son had it backwards, so I now have a LARGE supply of standard small pistol primers and a small supply of SPM. Obviously slow burning magnum powders such as H110, etc will require the use of SPMs in the .357. I've used standard SP in .357 with mid-range powders such as Unique, but never velocity tested or shot for small groups. How much would I be losing with fast-medium Alliant powders or Unique in the .357 with a SP?

Couple minor things, but on the bright side I now have probably a 10 years supply of primers, HP-38, Unique, and 2 lb each of Bullseye and Power Pistol to experiment with. All but the Unique and a few hundred bonus LR primers are in the most modern packaging, so no worries about age. One open cardboard can of Hercules Unique I am currently stuffing into .38s for a mild load to use up first. Smell and visual check out. The widow and SS were happy it was all going to someone who would enjoy it. Wanted the big pile of bullets, but the SS is an avid cartridge BP shooter, so he's already planning to convert them into bullets for his use.
 
I use standard primers for all powders other than H110 I've tried in .357, including 2400. No issues. As far as velocity, if you're not loading H110 and are using Unique or another faster powder you're likely not seeking top numbers anyway so using standard primers is going to be a non issue.

IMO
 
Others have already addressed spp vs spmp the issues. Not really a factor in target loads.
And you can’t have enough HP38! It’s a great pistol powder!
I would take advantage of this deal in an A-FIB heartbeat! Wish I had a chance at those 1-2 cent primers!
Do your load testing of them now btshtf so you’ll be ready! I’m still using rifle primers from the 80s! (bc I don’t do a lot of rifles anymore)
 
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