Re: 7.62x39 Small Primer Brass
For a small capacity case such as the one you lise, SR primers help reduce ES / SD in theory. This is because most (rem 7 1/2 has nearly as much as most LR primers) SR primers have a good bit less FLASH energy when ignited. Too much flash energy tends to cause problems accuracy wise, not to say that it is horribly bad. But Just The Right amount of flash to get the job done is considered to set up an optimal burn, thus it will tend to give better accuracy and lower ES / SD. Also, the small rifle primers can help with case head strength and handle higher pressures a little bit better.
All this being said, the Wolf LR primers is considered by most to generally "Cure The Problem" of too much flash from a LR primer by its being a fairly mild LR primer. Also, SR primers seem to be best in small capacity cases like your 7.62x39, or a 6BR case ect. In full sized 308 cases such as the 308 Lapua Palma it can cause missfires. This information about miss fires from the new 308 palma cases comes directly from Lapua in fact. Though right at the moment I can not find the link. When I do find it, I will edit and post it for you.
So, if you have LR cases in 7.62x39 I would honestly suggest you try some Russian -- Wolf -- or Tula primers. They really are a milder primer than any of the typical american primers, so for this type application they would fit the bill nicely. They are actually kind of like the RWS primers, in that they are Just Mild Enough, But Not too Mild for most mid sized cases. Say 30-06 on down, and most especially 308 sized cases.
Have a good one,
Gary
