Slamfire's of the opinion that a manufacturer should build his firearm so the firing pin strike is in the middle of the primer. That would be great.
But it also means case makers need to have their primer pockets exactly in the middle of the case. And case wall thickness be exactly the same all the way around. Plus zero fit tolerance in the bolt body to the receiver boltway.
Then the barrel tenon threads have to be exactly centered with the boltway axis. The hole in the bolt face has to be dead centered there. And the bold shroud around the bolt face has to be exactly the same diameter of the case rims used.
Finally, the case body diameter in front of the extractor groove has to be the same diameter as the chamber at that point so it centers perfectly at that point.
I may have forgot one or other dimensional issue that has to have zero tolerance, if so, sorry 'bout that.
If we lived in a perfect world all would be perfect. The offset does not have to be less than the wave length of an electron. For me, if the strike appears to be in the center, that is good enough for me. If the strike is obviously off center, that is too much.
So how far off center a firing pin strike is acceptable to you?