To paraphrase, trying to guess chamber pressure by checking out the primers is like looking to guess how deep a lake is by sticking your toe in the water. so do as you think that ideal. If you are firing the M1 Garand I might counsel using "armed forces" primers https://winchestersmallpistolprim59044.like-blogs.com/31721827/indicators-on-federal-primers-large-rifle-magnum-you-should-know