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Discussion Starter · #1 · (Edited)
DISREGARD THIS THREAD. I USED THE CALIPERS INCORRECTLY! SORRY TO WASTE ANYBODY'S TIME!! I am editing this thread because I must have been using the caliper incorrectly. Both sides of the grooves are actually very close, about a half a thousand different.

I tapped a slightly oversize bullet through the bore of my newest #4, a Maltby 1944 with a five groove barrel. I asked a question in a recent thread re: how to determine groove diameter when a land is opposite a groove. Received some good suggestions but when I examined the slug under 10X magnification I discovered something interesting. One side of each groove is noticeably deeper than the other side. I have a digital caliper and measured the depth on each side and came up with .005" on one side and .009" on the other. Each groove came out the same. Was the rifling broach deliberately machined that way or has the barrel worn that way? The bore is in excellent shape i.e. no frosting, sharp corners on the rifling, very nice visually, groove diameter is close to .313" as best as I can tell so far.
I am editing this thread because I must have been using the caliper incorrectly. Both sides of the grooves are actually very close, about a half a thousand different.
 
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