Iowabucks44

There is a definite possibility that a 209 primer could move the projectile a distance off the powder before the ignition of the powder, creating the possibility of several problems in your barrel.

I believe the real key in the equation is the condition of the powder in the bore. If for some reason you do not get instant ignition of the powder charge - such a hangfire, damp powder, clogged brrech plug - you really could move the projectile up the bore and off the powder with the detonation of the primer.

I choose to use the coolest 209 primer I can find that provides 100% ignition of the powder I choose to use. I have found that using different primers with the same load and projectile can move the POI of impact but I have not found the case where primers effect the group size - if the powder is 100%