I finally got around to ordering a .30 caliber muzzle erosion gauge and measured the muzzle diameter of my M1917 Winchester. It accepted the .3015 ring which was a little surprising since the throat erosion on this barrel is nearly zero. I have no trouble hitting targets at 100 yards with 150 gr. FMJ boat tails so the rifle is still very accurate even with a loose muzzle.

Merc