Zrex,
Good question that there may be no difinitive answer to.
My 243 and 270 will group tight right after a cleaning and throughout the range session.
My 30-30 and my 22lr need 1 or 2 shots to start shooting.

I will tell you this though.My 243 was like that too.When i started muzzleloading recently i learned to swab the barrel before shooting again which removed all the gun oil. I began doing that with the 243 and it started shooting well at the first shot. The 30-30 and the 22lr did not however