Primer Explosive Power Ranking


December 27, 2011, 02:39 AM
I got my brass, bullet mold, and dies for my new .45-70 (Marlin 1895GS) in the other day, so I decided to cast some bullets the other night. I ended up casting 150 of them with the 2 chamber Lee 405 gr mold, water quenching the bullets as they dropped out of the mold. I let them dry overnight and while spread out on a paper towel and tumble lubed them with Lee alox today. So, I'm ready to start loading them and what do I discover? I don't have any large rifle (LR) or large rifle magnum (LRM) primers! All I have is SPM and LPM primers. So, this brings up the question...

I know that the metal is thicker in the rifle primers than it is in the pistol primers, but how about the "spark" rankings of all of the types of primers?

Of the various types of primers for pistols and rifles (SP, SPM, LP, LPM, SR, SRM, LR, LRM), what order do they go in with respect to the amount of "spark" that they produce?

If you enjoyed reading about "Primer Explosive Power Ranking" here in archive, you'll LOVE our community. Come join today for the full version!
December 27, 2011, 04:14 AM
This might not answer your question completely but as far as temp/spark LR CCI BR and RWS are the coolest with Federal Match and WW being the hottest. Remington 9 1/2 also leans towards hotter. I wouldnt recommend trying to use the LPM primers for your 45-70 if thats what your thinking of trying. The cup is deeper on large rifle than large pistol so the pistol primer will seat too deep into the case. The WW or Federal Match would both be good primers to start with.

December 27, 2011, 05:53 AM
For 45-70 you need large rifle primers, just like the books will tell you. LR magnums could work if you adjust powder charges downward accordingly, but pistol primers are not the answer.

December 27, 2011, 09:46 AM
They will light the powder as long as your fireing pin will reach them but won't handle the pressure that LRP will. I use them in low pressure loads or when working up a unknown powder so I know when to start slowing down because I can see when the pressure starts coming up sooner. When the LPP starts showing pressure I switch to LRP & go slow incase of spikes. For the low pressure loads I get better groups with them(have no idea why).

December 27, 2011, 11:31 AM
During the Great Primer Shortage I used LP primers for shooting reduced cast bullet loads. Since the 45-70 is a relatively low pressure round I don't see why LP primers wouldn't work in a pinch. Hey, LP primers handle 44 Mag pressure, SAAMI spec is 36,000 PSI. 45-70 SAAMI pressure is 28,000 PSI.

December 27, 2011, 12:53 PM
Large rifle primers are deeper than large pistol primers. If you use LP and seat them properly, you're going to wind up with primers that are about .005 too deep in the primer pocket. This may or may not work, depending on your firing pin and chamber dimensions.

It's not like you can forever escape the need for LR primers, so why not run down and buy some and be done with the problem?

December 27, 2011, 01:48 PM
I've already done some searching on the web and I've seen incidences where people have used LP, LPM, LR, and LRM in the .45-70, so I don't have any problem with using LP or LPM for the first few loads with 13gr of Red Dot while I'm deciding on the *right* powder to order. Of course, since I'm ordering powder, I'll get 5000 LR and 5000 LRM primers while I'm at it to make up for the HAZMAT charge. I just haven't decided exactly which powder to get, so I haven't made the order.

In the meantime though, I was curious about the amount of spark that each of the primers could generate.

I figure that the following assumptions are probably true for any single brand of primers:


But that's not enough to fully order the list...

I've searched the web, but I just have not found anywhere that says how all the primers compared against each other.

It kind of boils down to whether a SPM is hotter than a SR and a LPM is hotter than a LR. If this is true, the list of primer power would be like this:

1. SP
2. SR
3. SPM
4. SRM
5. LP
6. LR
7. LPM
8. LRM

Of course, this ranking is assuming that any large primer is greater than any small primer...

Maybe it's just an academic exercise, but I haven't seen it published anywhere, so I thought I might propose it here, just in case anyone has ever come across the information or had done any testing on their own...

December 27, 2011, 02:00 PM
Someone posted a nice picture on here showing different primers ignited & looks like it depends more on brand then size.

December 27, 2011, 02:07 PM A little bit of info on primers...

December 27, 2011, 02:55 PM
Maybe these links will help.

Primer Flash Test Photos (

Primer Testing Reference (



December 27, 2011, 02:58 PM
Someone posted a nice picture on here showing different primers ignited & looks like it depends more on brand then size.
I have read posts where people have said that for brand X and brand Y, brand X's SP was hotter than brand Y's SR, or even that brand X's SPM was less than brand Y's SP, but I'm just talking about the same brand, not mixing brands. If you start mixing brands, that totally complicates the issue. You would need a list of all the combinations of brands and primer sizes, so assuming just Remington, Federal, Winchester, CCI, Tula, and Wolf, it would be 48 different primers that you would have to sort into relative "spark" potential. I've seen lists this long for the various pistol and rifle powders, but never for primers of evan a single brand, much less all 6 of those brands...

December 27, 2011, 03:15 PM
Then what is the point if a small rifle primer is hotter then a large rifle magnum if it won't fit?

December 27, 2011, 03:59 PM
There has been brass made that used different sizes of primers for the same caliber. I believe that I've seen this in .45ACP before. It's not been common, but when you encounter one after trying to put a LP into a SP hole, you notice it...

If you enjoyed reading about "Primer Explosive Power Ranking" here in archive, you'll LOVE our community. Come join today for the full version!