Always use military-type primers if you reload for rifles with free-floating firing pins.
The indentation you're seeing, given a softer civilian primer, could lead to a slamfire.
At this point, the nay-sayers will chime in and say they've been reloading for years with standard primers with no ill effects.  All well and good.
Fact is they've been at a least a little lucky.  Rifles with free-floating firing pins (mostly military semi-autos) were designed to be used with military ammo having military-spec primers.
Having witnessed a slamfire, I don't want that to happen to me or anybody else for that matter.
And yes, it was a reload using a standard primer.

And even WITH military primers, it is strongly recommended that you not cycle live ammo through your rifle unless you are on a range with your weapon pointed downrange.  You could get that one-in-a-million over-sensitive primer, and end up sending a bullet in an unintended direction, with potentially horrible consequences.

Find a reloader and have him make up some primer and powder-less dummy rounds.

-Troy