Flattened primers with no other pressure signs?

Just curious if anybody else has ever ran into this before. I loaded up some virgin 300 WM ADG brass the other day with h-1000 and 215 Berger's. My normal load is 76.5 grains in Winchester brass and 78 grn in Norma or nosler.

I started low like I always do in unknown brass, 71.5 grn and fired 3. Velocity was higher then I expected but still low compared to my usual node. Primers were flattened but zero hard bolt lift or case head marks. I continued up in charge weight with the same results. Effortless bolt lift and not even the faintest of head marks but pretty darn flat primers.

I have never flattened primers like this before even in overpressure loads that made the bolt sticky and made swipes on heads.

Thoughts?

Somewhat common when forming new (shorter) brass to your chamber. I wouldn't worry, unless it happens on your twice fired brass.

Winchester primers do that to me. Always flat no matter the charge

dok7mm said:

Somewhat common when forming new (shorter) brass to your chamber. I wouldn't worry, unless it happens on your twice fired brass.

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That's kinda what I was thinking just hadn't seen it to this extent before. The ADG wasn't as undersized as Winchester is and I haven't seen this in Winchester so that threw me off. Thanks. I'll neck size a few pieces and see what it does on the second firing.

ADG pressures faster than most other brass. tested it twice with two different lots of 300 win mag. plan on a reduced load

If you were using Federal primers they are known for softer primer cup material and prone to more flattening.

can1010 said:

ADG pressures faster than most other brass. tested it twice with two different lots of 300 win mag. plan on a reduced load

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Ya I had heard it did, it's certainly heavy so I started with what I though was pretty low on charge weight. It shot the same velocity as my Win brass load with 2.5 grains less so Im going to neck size a few with that charge and see what the primers look like.

Were the primers cratered as well? Or just flattened?

Common with new brass.

It's not a pressure problem.

There are other signs that reveal pressure long before flattened primers related to pressure arise.
Cratered primers reveal poor craftsmanship not pressure.

gohring3006 said:

There are other signs that reveal pressure long before flattened primers related to pressure arise.
Cratered primers reveal poor craftsmanship not pressure.

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Yep. That's why I asked. OP didn't tell us the details on the rifle. I was trying to see if there was an issue with something other then the brass.

CJS-6.5 said:

Were the primers cratered as well? Or just flattened?

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No cratering at all. Lone Peak razor action, Proof carbon. Round count is around 400. They are pancake flat, like no radius visible.

I wasn't terrible worried it was a pressure issue, hence why I kept working up. Just never seen anything quite like it even with loads that were in the "too hot" zone.

Ckleeves said:

No cratering at all. Lone Peak razor action, Proof carbon. Round count is around 400. They are pancake flat, like no radius visible.

I wasn't terrible worried it was a pressure issue, hence why I kept working up. Just never seen anything quite like it even with loads that were in the "too hot" zone.

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There's a good chance your work up will be the same after you fireform your brass.
Depending on how much shoulder set back you do. I don't get serious with brass until the third firing with neck size only. I usually see flat primers on the new brass. After I get the brass "stabile" I get serious with load development.