For reloading .223, is it Small Rifle Primers OR Small Rifle MAGNUM Primers?
Lyman 49 says SRP
Lee says SRP
I've seen some posts on forums that say that the primer cup is too thin on SRP for .223/5.56 rifles that are military spec and that for those rifles one must use SRMP. But everyone always proclaims to the heavens that one should "read your loading manual and follow what the manual says..."
I will be reloading for AR-15 rifles, chamber, throat, and neck checked and verified as 5.56. I will be using once fired .223 brass. I will be using Montana Gold 55 gr FMJ bullets and Winchester 748 powder.
So, which is it? SRP or SRMP ?
As an aside, I wonder if some of the primer cup piercing that has been described with SRP and mil spec AR-15's is actually due to the use of 5.56 brass in chambers that are marked "223/5.56" but are not really true to that marking. Many manufacturers use barrels that are marked capable of handling 5.56 but in reality the chamber is actually just 223. Some interesting links regarding this issue of falsely labeled "5.56" barrels can be found here:
(When you get to that page, click on ".223/5.56? Gage" and "5.56 Reamer" for more info)