Greetings Micky and Scout,
That was my thinking. Some data for the two groove barrels that I found gave the bore at .304" and the groove from .316" to .318". The dimensions were developed to suit the Mk VII projectile and gave decent accuracy and long barrel life. Tests with the 175 grain Hornady round nose often give two shots touching at 60 metres but different lots of projectiles can give quite different points of impact. Current production has a blunter shape.
Regards Grandpamac.
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