I'm glad you mentioned that Mk7 because there was a lot of .303" Mk7z ammo issued in 30 round belts during the 80's/90's for Cadet Forces. There was no restriction on its use in rifles and I used loads while range testing and zeroing. It just shot like normal .303" Mk7 ball to me although I have to admit that I'm not an ammo conniseur, just a prolific waster of it!
