I'm trying to figure out why I have primers that are flattening out. Usually, I consider this to be from excess pressure, or excess headspace. As I mic the rounds after firing them, and only set the shoulder back about .002 for each rifle, I don't think it is excess headspace.
I'm using 30.4 grains of AA2520 with a 123 grain Lapua Scenar. Brass is trimmed after every sizing before loading, so I know I'm not jamming the neck into the throat.
I have cleaned the rifles with Sweet's 7.62, used a brush, cleaned again to insure I have all carbon, copper, and powder fouling out of the barrels.
The bullet was seated to 2.260, but unfired rounds came out of the rifle with the rifling engraved onto the bullet. So, I have seated the bullet deeper into the case. I check bullet depth by using candle soot on dummy rounds to find the right depth for the bullet.
Both my AA Shilen barrel, and my Lothar Walther barrel show the same primer flattening. I switched to AA2520 because my load of W748 showed the same thing, even with velocity at 2430 fps out of my 19.5 inch barrel (30.3 grains).
I'm using Lapua cases, CCI450 primers, Lapua 123 grain scenar bullets. Velocity through the 19.5 inch AA Shilen barrel is 2482, 2498, 2502, 2505 fps. The factory load is over 2600 with a higher powder charge. Velocity through the 18 inch Lothar Walther barrel is about 45 fps lower.
Primer pockets remain really tight, and brass loss from cracked necks and other causes is the same as it has always been. The brass has been reloaded a number of times, and necks have been annealed.
My velocity levels indicate that I am right where I should be with that powder charge. If I were over pressure, I would at least think I would be getting more velocity. I load for accuracy, not velocity if that matters.
Any ideas on what is happening? Maybe some minor primer flattening is normal, and I shouldn't worry about it. The primers aren't completely flat, none are pierced, none flow back into the firing pin hole.