Muzzle Wear: Criterion Barrel

[MoMallard]

I recently had the CMP custom shop put together a BEAUTIFUL 1903 1941 USMC Sniper clone. Shoots like a dream. When I received it, I gave it a cursory check that included a MW/TE measurement. It had a ZERO muzzle and a 1 or so throat upon receipt. After firing EXACTLY 489 rounds, the MW reading is now a 1. I would not have expected this much change after such a minimal round count. No. It is not over exuberant cleaning rod wear. Thoughts?

[Parashooter]

Most likely explanation is that firing cleaned out some burrs left by the crowning operation. Think about what is being measured by the tapered gauge and it should be clear how a small burr can affect its reading. (Note that the usual tapered gauge measures the land-land diameter only at the specific point where the crown intersects the bore, telling absolutely nothing about that dimension even .010" farther into the barrel. It's entirely possible your barrel has a uniform bore diameter of .301" or so - a perfectly acceptable condition as long as one doesn't think a "muzzle wear gauge" is actually measuring muzzle wear.)

[MoMallard]

Thanks Para. That makes absolute sense.

[PhillipM]

Your gauge should be your target grouping.