MountainDevil54
there wont be pressure once the firing pin is adjusted.
I really hope you know enough about the operation of a gun, any gun, to know that there is always pressure on the nose of the primer at the time immediately following the setting off of the charge. Centerfire shooters, reloaders in specific, look for the signs on the primer indicating high pressure. It is statements like this that really makes a knowing person question your credibility.
Anyway, I really believe you are wrong. There will always be blow back pressure on the nose of the primer from the charge going off. There has to be. It really does not matter what the headspace is. Pressure is there and if there is enough it will push the primer into the face of the bolt or frame hard enough to make an impression. Head space has nothing to do with that effect.
There is no difference between the centerfire and a ML in this case.
The amount of the pressure will be detirmined by the size of the charge, the weight of the projectile. the length of the barrel, how tight the projectile is in the bore, and the size of the flash hole. All of these add up to back pressure on the primer.
And even though you might not believe me I hope enough other folks read this and tell you close to the same thing.
I hope this make some sense to you, because ignoring this could get you hurt.