Primer Cup Hardness?

Is there any actual study information on primer cup hardness. Every search that I have done tells you the cup thickness but not the hardness.

I have had a few slam fires using Winchester Small Rifle primers in my AR. They are seated correctly and deep enough but still having issues. The slam fire only occurs during the single load slow fire stages of high power. Never had a slam fire during the rapid fire strings even though I am still using the WSR primers. Also never had a slam fire with the Remington 7 1/2 primers on the single load strings. Just hate to condemn the WSR primers as I have a bunch of them.

I used CCI #41's since I started reloading
.223 for that exact reason. They are supposed to have a harder cup. You pay a little extra but I've never had a slam fire. I use CCI exclusively due to experiencing issues with other manufacturers. The standard CCI small rifle primers seem to be slightly harder in nature as well.

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Originally Posted by CodySPowell

I used CCI #41's since I started reloading
.223 for that exact reason. They are supposed to have a harder cup. You pay a little extra but I've never had a slam fire. I use CCI exclusively due to experiencing issues with other manufacturers. The standard CCI small rifle primers seem to be slightly harder in nature as well.

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I agree with Cody. I only use CCI myself.

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Originally Posted by dand38s

Is there any actual study information on primer cup hardness. Every search that I have done tells you the cup thickness but not the hardness.

I have had a few slam fires using Winchester Small Rifle primers in my AR. They are seated correctly and deep enough but still having issues. The slam fire only occurs during the single load slow fire stages of high power. Never had a slam fire during the rapid fire strings even though I am still using the WSR primers. Also never had a slam fire with the Remington 7 1/2 primers on the single load strings. Just hate to condemn the WSR primers as I have a bunch of them.

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Interesting timing as I ran across this FAQ on the white ok site today. Has a discussion on WSR primers

https://www.whiteoakarmament.com/resources/faq.html



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I haven’t seen an independent study on primer harness, but I do know that manufacturers study this. SAAMI gives guidelines on how to test Primers. This involves seating a primer in a case and dropping a steel ball on a firing pin. The height of the steel ball determines the amount of force delivered to the firing pin.

The tests are caliber specific. A large sample (usually 100 tests) are done to statistically analyzed the primer. This test helps to weed out Primers that are both overly sensitive or Primers that are not sensitive enough.

Manufactures of Primers make many different types of Primers within a given size and type. Altering primer cup thickness, the mix and charge amount, as well as anvil design in order to comply with SAAMI standards. (If they are SAAMI member company or follow SAAMI guidelines). Only a very small amount are available to the Reloading market.

A particular case study, that I was involved with, was done on 300BLK which has a high misfire rate due to the very small shoulder. A term called “crush up” is used to describe the tendency for the firing pin’s force to be absorbed by the flexing of the small and thin shoulder. All cartridges that head space on the shoulder have a similar phenomenon but the 300Blk is especially bad due to the design of the case.

Adjustment to the case design as well as the primer had to be made in order to reduce the misfire rate. Obviously as a handloader these Primers and cases aren’t available to us. However it does show that if we are having issues with slam fires, pierced Primers, and duds. That we may need to look at the primer rather then blaming ourselves or the firearm.



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I’ve read online, since the beginning of on line, that cci has the hardest cups, followed by remington, then winchester and federal with the softest. I have never seen an actual real test or any actual data on it though.


JTD

I have always head/read that 41s were the best way to prevent slamfires in semi auto riles. That said I have loaded and shot north of 10 k WSR primers in ar's and mini 14s and have yet to have a slam fire. Maybe I am just lucky, or maybe there is another issue. Try shooting some of your loads in another ar. If problem occurs it has something to do with the ammo. If not it is the rifle. Then try another bcg. My guess would be firing pin is binding in the bolt or possible has too much protrusion.

Thanks for the advise. Giving me some things to think about. This is the same BCG that I used in my previous match rifle. I never had an issue in that rifle. Both had a 223 Wylde chamber. I think that I will just transfer over to CCI and Remington Bench Rest primers and see if my slam fire issue changes.

I shoot mostly Federal and have never had a slam fire. I shoot standard and AR small rifle primers.