Flat primers, factory load, why???

[mdmp5]

So I checked some 1x fired .300 win mag brass. I should've noticed this earlier, but the spent primers look pretty flat to me. Should this be happening with factory loads? The load is:
Hornady TAP 178 gr AMAX (estimated 2960 fps)

Rifle: Rem 700P 26"

I'll post some pics of the brass when I get home

 

[Kinsman]

Re: Flat primers, factory load, why???

Not unusual in my Savage. 300WM is pretty hot.

 

[9H_Cracka]

Re: Flat primers, factory load, why???

Belted magnums headspace off the belt for the first firing, creating excess headspace between the shoulder and the bolt face when fired. You can take a mild load, push the shoulder way back so that the case moves back to the bolt as it is fired, and the primer will flow quite a bit and produce a very flat primer that shows the appearance of over pressure.

Most likely this is all that is going on with you. If you now headspace off the shoulder in your rifle, duplicate the velocity with an appropriate powder, I suspect your primers will look just fine.

A better indication of pressure issues with the ammo in your rifle would be an ejector wipe.

 

[ChadTRG42]

Re: Flat primers, factory load, why???

Flattened primers could mean a soft primer cup. It doesn't mean for sure that there is excessive pressure. Is there any shiny spots on the case head or sticky bolt lift when shooting this ammo?