Primer Substitutions
By Mitchel Demand
I do not need to tell any of you about the shortages we have in ammunition and reloading supplies. We can all see it every time we walk into a sporting goods store or gun shop. Because primers are so hard to find we have been getting quite a few questions about substituting primers in the loading process. Here is a chart of primer dimensions just to get us started. This chart came right off the SAMMI website.
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
Comments (22)
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I would like to know if large magnum rifle primers can be used in place of large rifle primers safely.
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I use small rifle primers in 38 special alot and have had no problems. Cant tell the difference.
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The last paragraph states “It is possible to substitute LRP for small pistol magnum primers…” . Shouldn’t that state “possible to substitute SRP for small pistol magnum primers…”
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Is this a misprint (from Sierra text above)? : “It is possible to substitute LRP for Small Pistol Magnum Primers in certain situations”??
How can LRP(RIFLE) be substituted for small PISTOL mag primer?
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It is possible to substitute LRP for Small Pistol Magnum Primers in certain situations if the certified loading data supports it.
Do you state this on your website? How is it possible if an SPM is of smaller dimensions than an LRP?
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In your opinion, can a Large Magnum Pistol primer be safe enough to be used as a Large Rifle primer?
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Where can I find 70 grain .243 SMK’s ? If unavailable then when will they be?
Sorry for this unending question but I am desperate for this summer shooting season. -
According to the CCI site the SRP and SPP are exactly the same (same diameter, same cup thickness and same depth) and can be substituted without risk.
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Please correct the typo in the last sentence; ” It is possible to substitute SRP for Small Pistol Magnum Primers in certain situations if the certified loading data supports it.”
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small rifle primers are used in the 454 casull
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Great information
Thank You -
Mitchell, I have read your article on Primer Substitutions. I bought an Armscor Precision 22 TCM rifle with a 22” barrel for my granddaughter. Factory ammo uses SPP but since I’m reloading for a rifle, in your opinion, would it be safe to use SRP in this cartridge for this rifle?
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It appears that the last line of this article should be amended. The phrase “substitute LRP for Small Pistol Magnum Primers” should be amended to read “substitute SRP for Small Rifle Magnum Primers”. It should be impossible to place any Large Primer into any Small Primer pocket, I believe. If I am wrong, feel free to delete my post, and accept my apologies. Henry42
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Hello Mitchell,
Excellent info. I have been handloading since 1983. I have loading manuals for each manufacture’s bullet I load.
I have not damaged a weapon since I started loading. Nobody knows more about a bullet than the ones that make it.
I will listen to you. Small pistol magnum primers I had to wait on for six months and now I believe it will become an even longer waiting period. I’m loading .357 magnum. No technical data for using small rifle primer for the.357 magnum cartridges put me in the field of the unknown. I have a chronograph and a Thompson Contender w/10″ .357 mag for testing and if they do well, these test rounds will go in my one of two Ruger Security sixes. Both have standard hammer springs.
When I get a chance to test this, I will let you know my velocities and primer condition. Thanks. -
Question: can a primer of same size and of same magnitude be substituted with another from a different company? Examples: substituting Federal small rifle 205 for Winchester small rifle WSR, or Remington small rifle 6 1/2 for WSR. Thank you!
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“It is possible to substitute LRP for Small Pistol Magnum Primers…..”.
Looks like a typo to me, as Mitchell(Mitchel, sp?) certainly did not mean to write this substitution. LRP should be SRP in this line as I see it. Good article with good information.
Thanks. -
Typo?
“it is possible to substitute LRP for Small Pistol Mag”
You meant SRP, not LRP, right?
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It is possible to substitute LRP for Small Pistol Magnum Primers in certain situations if the certified loading data supports it.
Did you mean sub SRP for SPM?
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You conclude: “It is possible to substitute LRP for Small Pistol Magnum Primers in certain situations if the certified loading data supports it.”
Didn’t you mean it it possible to substitute SRP (Small Rifle Primer)……
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Nice explanation.
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can i use SRP in 9mm loading under max?
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