To add a bit to what Toby said on the Not for Ball versus Choke. My understanding the Not for Ball mark had originated on the basis that prior to choke boring a standard practice had been to load a ball of about .010" under bore size. If you shot this size ball through a barrel having a full choke of around .040" Constriction you were virtually guaranteed a bulged barrel at the choke. Shooting ball through a choke was OK as long as The Ball would pass through the choke. My understanding was the proof houses recognized the NFB mark was causing confusion & many were taking it that No Ball could be fired through a choke bored barrel, regardless of its size & that the gun would be "Out of Proof" if so used.
Miller, that is really interesting, never heard such a concise description of why the decision was made to drop the NFB.
