Home Forums Reloading Reloading Software magazine box c o l mauser

i'm putting together an FN mauser cking for feeding problems, cartridges I have loaded are to long. My question is how much less should my col be than the magazine box to account for bullet movement in the cartridges in the box from recoil. wouldn't want a fail to feed in the heat of the action. or am I over thinking this?

found some factory loads feeds, just fine.