10mm using Large Rifle Primers

T

TriggR

New member
Okay here goes I just started loading 10mm using large rifle primers due to necessity. And I really don't want to hear that they're .004 longer than large pistol primers, isn't the 10mm a cut-down rifle cartridge. They fit perfectly in my setup they work perfectly after 150 test rounds.
I have also watched a number of reloading companies videos where they have pressure-tested different cartridges using both large pistol and large rifle and small pistol and small rifle there was no noticeable difference in pressures.
I did run the cronograph and there wasn't one bit of difference in bullet speed so that would tend to make me believe that the pressures would be very close everything else staying the same. Why do some people post saying I wouldn't do that they're longer they have done no research or testing on their own
Federal 210 mixed brass
 
Why do some people post saying I wouldn't do that they're longer they have done no research...
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...because rifle primers are higher, and do stand proud of the base of the case, which in an auto can be... a concern.
 
I have also been using small rifle primers and my 9 mm and I also noticed no difference on the Chrono
 
IF your brass has primer pockets deep enough to accept rifle primes seated to proper depth, fine. Not all pistol brass using large primers does.

If your gun's firing mechanism has enough power to reliably ignite rifle primers, fine. Not all guns do.

Most of the advice given, particularly on the internet, is people simply repeating something they heard. Sometimes it applies to your specific situation, sometimes not so much.

Also be aware that someone else's tests, with their gun, their components and their specific combination of factors does not guarantee you will have identical results.

Expecting similar results is reasonable, but always be prepared for results that are at either extreme end of the bell curve, until you have tested your equipment to see what you actually get.
 
Totally agree I did do some research and I did the testing. If my primers don't seat in all the way they won't come out of the shell holder
 
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Yes there have been tests done with small pistol, small pistol magnum, and small rifle with minimal variation. They have identical primer pocket dimensions.

I have yet to see a study where large rifle and large pistol were swapped.

They are different in height. Sorry but it is what it is. Primers are generally supposed to be seated below flush. While you might be getting them to flush that is still higher than reccomended for an auto loader. And most shell holders have some wiggle room built in. Whether or not it slides out is not a proper gauge of whether a primer is properly seated or not.

Regargless of what 10mm was originally based on, I would be willing to bet they are not made from other cases anymore, especiall ones that are now obsolete. They are make as 10mm cases with large pistol primer pockets.

Im honestly not sure why you are asking, as it seems you have already made your mind up and are bound and determined to keep doing it.

My advice would be to stop doing it, it is unwise at best, especially considering your using mixed brass.
 
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Exactly what Shadow said however if you are bound and determined to do it anyway please either shoot alone or advise those around you that the ammunition in question my "auto fire" when the slide closes on a high or "proud" primer and that second or third or more shot occurs.
I promise you it will at the very least surprise you or God forbid you injure or wound another person.

Don't listen-that's your call but you have been given EXCELLENT advice.
Seems as though some people only learn the hard way.
 
Manufacturers have pretty smart folks. If there were no differences in Pistol and Rifle pressures, I'm sure they would just have a Large and a Large Magnum designation.
 
isn't the 10mm a cut-down rifle cartridge.
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No. It was a new pistol cartridge developed by Norma for the Bren Ten.

If you can seat large rifle primers flush or below, that is due to tolerances in the primers and primer pockets and maybe a heavy hand on the lever.
My Dillon Super 1050 primes to a hard mechanical stop with a lot of leverage and will sock rifle primers down flush or below in .45 ACP, so it can be done.
As 44 AMP says, if it works it works, but it is your responsibility making up loads "off label."
 
10mm is a cut down rifle round does not stick up at all or it wouldn't come out of my priming setup
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I don't know the history of the 10mm but for the sake of this discussion lets say the 10mm was derived by cutting down a rifle case . That in no way means that's how the 10mm cases are made now . I'm sure they are made from scratch specifically for the 10mm now . This "should" mean the primer pockets are specked out for a specific primer . This leads me to ask the question , why would/are the load manuals recommending a LP primer in a cartridge that has LR primer pocket dimensions ? This would seem to me to give you .004 below flush just as the primer bottoms out . We then generally are told to ( I forget the term ) put a load on the cup which compresses the cup another .002 or .003 . Meaning "if" the 10mm primer pocket is designed to fit a LR primer , Seating a LP primer should always result in a .006+ below flush primer seat ????

Those of you that load 10mm , do your LP primers tend to seat way below flush ?

I'm not being snarky , truly trying to work this out in my head . :confused::)
 
According to the brief "bio" in one of my Hornady manuals, the 10mm Auto was developed by whit Collins, John Adams, and Irving Stone, with the assistance of Jeff Cooper.

They started out using a cut down .30 Remington (rifle) case and the 180gr bullet from the .38-40 cartridge, and developed the 10mm Auto from those.

Norma, and everyone else today making 10mm brass is not making them from cut down obsolete rifle cases.

If large rifle primers fit properly in your 10mm brass, I'd say that was serendipity, not something to be counted on as working every time.
 
In the S&B 10mm cases that I have used it takes all the force I can muster to seat a LP primer flush. I can't imagine trying to seat a LR primer in one of them.
 
TriggR said:
And I really don't want to hear that they're .004 longer than large pistol primers
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You won't because the difference is 0.009", and not 0.004". But even that's just the average value. You can see on page 26 of the SAAMI handgun cartridge standard that the tallest large pistol primer is 0.003" taller than the shortest large rifle primer, which is 0.123" tall, so there is some overlap. That means you can count on your pistol primer pockets being fine with the seating of at least some portion of the rifle primer population. Primer pockets can be a thousandth or two deeper than 0.0126" that so pistol primers can be sure to seat below flush when the bridge is properly set. This depends on the lot of brass. So, with a lot of different LR primers, you will find you still get a fit. However, the tallest LR primer in the tolerance range is 0.136", or what is probably 0.006" taller than you can be sure of having available with your pistol primer pockets. Primers that tall would stand proud of the face of the case head when you ran your finger over it, and would have the potential to fire during chambering, producing doubling or tripling (two or three round full-auto firing) or more. So you want to cull any like that. A high pistol primer may simply be seated deeper during chambering, but a high rifle primer may already have its anvil feet firmly against the floor of the primer pocket, and those are the ones to watch out for.

The bottom line is that you will get away with the physical substitution as long as you don't have a rifle primer lot that is near the tall end of the tolerance range.

Other issues to watch for are that rifle primers are intended to make more gas than pistol primers to produce adequate ignition start pressure in the larger empty space you find in a typical rifle case, so they can more readily unseat handgun bullets during powder ignition. The usual symptom this produces is an increase in velocity standard deviation, and that would be an indication this was happening. It is more likely in a case with a small powder space, like 40 S&W, so you'll have to measure the velocity SD difference you are getting to see if it's an issue. Also simply watch for bigger groups that would be due to irregular ignition changing the barrel time shot-to-shot.

Another factor is that some rifle primers have heavier cups, and where your self-loader may not have a problem, a revolver that has been tuned may not work reliably with rifle primers. Personally, I would check the cup thickness as compared to my large pistol primers and if I found a difference, I probably would not use rifle primers for a match or field loads where a stoppage could cause me a problem. A clue would be shallower primer indentations on the cases than I get with LP primers.
 
I agree with everyone maybe it's the lot I've got it's on the lower end of height again this is necessity and something that I have on hand 4 MI 7 mm Remington Magnum which I won't shoot 1,000 of I would prefer large pistol primers does anybody want to sell any
 
I have on hand 4 MI 7 mm Remington Magnum which I won't shoot 1,000 of I would prefer large pistol primers does anybody want to sell any
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Have you considered offering them for trade???

Sometimes, people are in the situation where the thing that they want and can't get is worth more to them than cash.

If I had a need for large rifle magnums (I don't), I might trade some of my large pistol primers for some, but I'm not selling any, because right now, cash doesn't get me more primers and would most likely get spent on something else useless, like, oh, food, or gasoline,.....:rolleyes::D
 
I just found this on sierra site, https://www.sierrabullets.com/primer-substitutions/
Pay close attention the the last paragraph at the end!

Let us start with Large Rifle Primers (LRP) vs Large Pistol Primers (LPP). Both are roughly the same diameter. This is where the similarity ends. The LRP is at least .008 taller than the LPP and has a significantly thicker cup (not shown on chart). This means a LRP will not seat flush or below the face of the case head in a pistol cartridge, thus creating a dangerous situation; However, the LPP will fit and seat in a LRP primer pocket, but it will seat too deep. Just because it fits does not mean it will work. The thinner cup of the LPP can be pierced by the firing pin of a rifle and harm the gun and its user. Also due to the slower burning powders in a rifle ammunition the charge from the LPP is insufficient for reliable use. In summary, do not substitute LPP for LRP at all, period.

Here is where math and physics can get you hurt. Small Pistol Primers (SPP) and Small Rifle Primers (SRP) are virtually identical in size as are the primer pockets of their respective cases. This does not mean that they can be substituted for each other. The SRP still has a much thicker cup and hotter ignition. There is no verifiable data for the difference in fire rate between the primers. Ask any of the primer manufacturers and they will not tell you. Been there done that. Here again a SPP should never be substituted for an SRP. I do realize there are times that one can use a SRP in place of a Small Pistol Magnum Primer. My issue with this, where is the data? How do we know it is safe? People say they have done it with no issues and good for them. In a revolver I can see giving it a try if one can find verifiable data. I certainly would not risk it with an unsupported chamber in a semi-auto pistol.

To sum it all up, do not substitute SPP for SRP or LPP for LRP at all, period. It is possible to substitute LRP for Small Pistol Magnum Primers in certain situations if the certified loading data supports it.

Have fun and stay safe
Mitchell

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emissary1911 said:
I just found this on sierra site, https://www.sierrabullets.com/primer-substitutions/
Pay close attention the the last paragraph at the end!

Let us start with Large Rifle Primers (LRP) vs Large Pistol Primers (LPP). Both are roughly the same diameter. This is where the similarity ends. The LRP is at least .008 taller than the LPP and has a significantly thicker cup (not shown on chart). This means a LRP will not seat flush or below the face of the case head in a pistol cartridge, thus creating a dangerous situation; However, the LPP will fit and seat in a LRP primer pocket, but it will seat too deep. Just because it fits does not mean it will work. The thinner cup of the LPP can be pierced by the firing pin of a rifle and harm the gun and its user. Also due to the slower burning powders in a rifle ammunition the charge from the LPP is insufficient for reliable use. In summary, do not substitute LPP for LRP at all, period.

Here is where math and physics can get you hurt. Small Pistol Primers (SPP) and Small Rifle Primers (SRP) are virtually identical in size as are the primer pockets of their respective cases. This does not mean that they can be substituted for each other. The SRP still has a much thicker cup and hotter ignition. There is no verifiable data for the difference in fire rate between the primers. Ask any of the primer manufacturers and they will not tell you. Been there done that. Here again a SPP should never be substituted for an SRP. I do realize there are times that one can use a SRP in place of a Small Pistol Magnum Primer. My issue with this, where is the data? How do we know it is safe? People say they have done it with no issues and good for them. In a revolver I can see giving it a try if one can find verifiable data. I certainly would not risk it with an unsupported chamber in a semi-auto pistol.

To sum it all up, do not substitute SPP for SRP or LPP for LRP at all, period. It is possible to substitute LRP for Small Pistol Magnum Primers in certain situations if the certified loading data supports it.

Have fun and stay safe
Mitchell

SHARE
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Here is the data for substituting Small Pistol, Small Rifle, and Magnum Pistol Primers for one another in pistol rounds.

https://www.youtube.com/watch?v=NGVRGsoOr6k
 
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