While you may get away with it Winchester does not release their MILSPEC primer to the public. They put them in their commercial ammo but for some reason don't release them. Winchester marketing is rather funny about things and unless there is public demand for something they tend to keep things in house. I put this on another forum a couple years back and asked people to write them and ask for them but apparently not enough did so.
If you say off the max loads you may avoid piercing the primer.
It is critical in loading that your primers be seated about .003" Min under the case head.
When you drop the bolt group on a round and extract the round you will see an indent on the primer. In the business it is referred to as a "tic" and up to a certain depth the primer will not fire.
When the ARs were first produced they had a striker that was much heavier and there were "tic offs" using standard small rifle primers. To correct this the MILSPEC primers with heavy cups were fabricated and the striker weight reduced an estimated 50%.
Many folks have ruined striker noses and bolt faces running standard small rifle primers and then there are those that have got away with it.
If you stay with 55 gr bullets and off the high end you may be fine but then again being a shooter I understand where you are trying to go. The Sierra 52 gr. HP will do nice things in your AR for the 100 yard matches and 200 yard matches.
You could shoot the 52s at 100 and 200 and get the MILSPECs for 300 and 600.
Remington BR primers are also heavy and the Wolf brand is available fabricated for the 223. I have 5M of them but have not loaded any as yet so I can't really tell you how they do but guys tell me they are fine. I am still working my way through the last of 10M of the Remingtons.
As a side note you might add Mobil 1 Synthetic Motor oil 0W20 or 0W30 to the gas ports on bolt and other lube areas. Mobil 1 will keep the carbon soft internally and make it much easier to clean.
The Army MTU has been using Mobil 1 for years. It is also good for M1As and Garands in the gas system to keep them from carboning up.
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