Converting .38 Special Brass to Take Large Pistol Primers

[DaveM]

One gap in my preps that has come to light in the aftermath of this year's panic caused by COVID19 and civil unrest is my stash of small pistol primers. I have around 2500 - 3000. If you've been paying attention, small pistol primers are currently unobtanium at anything resembling a reasonable price.

In contrast, I have at least 5000 large pistol primers, which I primarily use for .38-40, .44-40, and also Magtech brass shotshells.

One cartridge I load for is .38 Special. I have thousands of .38 Special empties, so the thought occurred to me that I could convert 50 - 100 to take large pistol primers.

When primers become more easily available I am planning on stocking up on them but in the interim I want to increase my options.

In doing a bit of online research, I learned that there used to be .38 brass produced with large primers. So, why not convert some .38s to large primer pockets?

So what is the best cutting tool to use to enlarge the primer pockets? I'm leaning in the direction of a .210" center cutting end mill, chucked in a drill chuck in the tailstock of my 7x14 mini lathe. The deprimed cases would be held in my lathe's chuck.

The other option for a cutting tool would be a Hornady #041211 Large Primer Pocket uniformer.

I am aware that changing from small to large pistol primers is likely to increase pressure, so for safety I'd be using mild .38 Special loads and doing any initial testing in revolvers chambered for .357 Magnum.

Has anyone tried this?

@Outpost75, I'm especially interested in your thoughts.

[Bazoo]

I am interested too, as I've had the idea for years. Mostly as an experiment than a need. I have a couple large primer 38 special cases. I could section one for reference as to thickness of web and such for comparison.

[elmacgyver0]

Should work fine.

[DaveM]

I am interested too, as I've had the idea for years. Mostly as an experiment than a need. I have a couple large primer 38 special cases. I could section one for reference as to thickness of web and such for comparison.

Thanks for the offer but I don't think it's necessary.

[Outpost75]

Tried to post on the other forum where you posted this question, but for some reason or other I have been banned over there with no explanation, and my posts deleted. Strange...

Anyway, there are large primer sized primer pocket "uniformers" which are designed to be run under power, but all I am aware of are dimensioned for large rifle primers, which have a greater cup height than pistol primers.

Attachment 270570

To enlarge a "small" sized primer pocket, I would select a drill gage which is a wee bit smaller than the diameter of the large primer pocket, and use this to heavy chamfer the small primer pocket in the case, to provide an entry for the appropriate sized end-mill or large primer pocket uniformer to be run under power. Set a depth stop so that you do not exceed the max. depth for the large pistol primer. Rigging a collect to securely hold .38/.357 cases for machining is a useful exercise, but once you figure this out the results should be rewarding.

Please update us on how you accomplish this and how it works out!

[la5676]

Ummmmm, what data are you gonna use for a large primer now used in place of the lighter small pistol primer. Are you gonna just back off 10% and hope it OK.

Why not just use small rifle primers. One of the bigger reloaders in our club told me recently he had inquired from "someone higher up" (who that is I don't know) but it's a straight across exchange. Then again, I've heard guys say they have had about half or more ftf with SR used in place if SP because of the harder cup material used.

I'll sit back now and learn something.

[dannyd]

Back in the 1930's both 38 Special and 357 Magnum used large primers.

[Outpost75]

A 10% charge reduction until you can measure velocity is good practIce. In comparing large vs. Small primer in .45 ACP I have found small pistol magnum equivalent to large pistol standard, or 10% charge reduction for large vs. Small primer.

[Bazoo]

From my research of SPP use in 45 acp, I don't think the difference between large and small primers would be enough to warrant any reduction in powder.

Sorry, didnt mean to contradict you outpost, we posted at the same time.

[gpidaho]

I'm far from a ballistics expert but if you are successful in making the primer pocket conversion, I wouldn't worry TOO much about the pressure difference small primer to large. As stated in the OP you'll be testing the loads in a 357. I've run a few pretty hot 38s from my Ruger GP100. You can always start with a low charge or seat the bullet out farther to lower pressure and then work up. Gp

[SweetMk]

I sure am glad I found that RCBS primer pocket swaging tool that goes in my reloading press,,

IT was lie $33 at a local LGS,, and I could not find it at all on line,,
If I gotta change primer size,, I am gonna need all the pocket resizing help I can get! LOL!!

[EDG]

The Remington # 6 1/2 has a softer cup for use in the smaller lower pressure rifle rounds so they might work more easily in the 38 Special.

I did a lot of lathe production work many years ago including boring small diameter holes.
I would try boring it with a 2 flute center cutting end mill used as a boring bar. Once the boring bar is cutting to the right diameter never change the setting of the cross slide unless to adjust the size of the hole.

[nicholst55]

Tried to post on the other forum where you posted this question, but for some reason or other I have been banned over there with no explanation, and my posts deleted. Strange...

Anyway, there are large primer sized primer pocket "uniformers" which are designed to be run under power, but all I am aware of are dimensioned for large rifle primers, which have a greater cup height than pistol primers.

Attachment 270570

To enlarge a "small" sized primer pocket, I would select a drill gage which is a wee bit smaller than the diameter of the large primer pocket, and use this to heavy chamfer the small primer pocket in the case, to provide an entry for the appropriate sized end-mill or large primer pocket uniformer to be run under power. Set a depth stop so that you do not exceed the max. depth for the large pistol primer. Rigging a collect to securely hold .38/.357 cases for machining is a useful exercise, but once you figure this out the results should be rewarding.

Please update us on how you accomplish this and how it works out!

Second to last item:

https://www.sinclairintl.com/reloadi...prod34720.aspx

[cwlongshot]

Good stuff!

CW

[dverna]

Seems like a reasonable approach. With a little lathe the time to convert 100 cases will not be too bad either. EDG's idea for boring the hole makes sense.

Looking forward to seeing your results.

[Froogal]

In case no one has noticed, ALL primers are unobtanium right now, as well as brass.

[cwlongshot]

In case no one has noticed, ALL primers are unobtanium right now, as well as brass.

Not when your prepared... I dont have any shortages.

CW

[DaveM]

Thanks guys. I did wind up ordered a 4 flute center cutting .210" end mill, which hopefully should arrive by next weekend.

[kootne]

From my experience, you will probably have a greater percentage of good cases if you cut slightly undersize and swage to finish dimension. A .210 endmill is not going to cut undersize, maybe it will cut .210 but probably is going to cut over unless everything is "right" and your machine is rigid and tight.
Second best way would be to use a smaller diameter cutter and bore rather than try to dead center an on-size endmill and drill with it. Use a dial indicator on your cross-slide to monitor actual position during your process.
If one way doesn't work and you can't resolve it, try something else. (called paying your dues)
Hope I didn't sound like too much of a Debbie Downer, It can be done and I wish you all the best.

[DaveM]

From my experience, you will probably have a greater percentage of good cases if you cut slightly undersize and swage to finish dimension. A .210 endmill is not going to cut undersize, maybe it will cut .210 but probably is going to cut over unless everything is "right" and your machine is rigid and tight.
Second best way would be to use a smaller diameter cutter and bore rather than try to dead center an on-size endmill and drill with it. Use a dial indicator on your cross-slide to monitor actual position during your process.
If one way doesn't work and you can't resolve it, try something else. (called paying your dues)
Hope I didn't sound like too much of a Debbie Downer, It can be done and I wish you all the best.

Thanks. I expect that there will be a learning curve. I'm not expecting it to necessarily work right off the bat. I have enough .38 empties that I can afford to lose a few.