Hi all, especially Rich and Andy.
Re the comment about the NRA, I can state that from research in the NRA's records that they never used rounds headstamped "KYNOCH .303" for the Imperial Meeting. All rifle ammunition for the main competitions was supplied by the War Office/MoD, free of charge, and was strictly military in origin. The only years that Kynoch ammunition was used were 1920/21/22 ( when it was "K15", and 1923, when it was "K 23".
KYNOCH 303 is strictly a commercial headstamp, and rounds with this may or may not have had the primer ring-crimped in, depending on the pressure that the round might develop, and Kynoch's feelings on the matter. I don't think there was any other significance to the matter.
Regards,
Roger.