Slugged the bore last night with a v-anvil and pins. Seems the bore diameter is .460 and the grove is .466-467, measured 10 inches from the breach. The right chamber had a very small burr next to the extractor which looked like a minute shaving. However, you could see the mark it left on the brass case. One pass with an extremely fine file took care of that problem. We then shaved off the bottom of the sizing die, which, to my surprise, had been previously machined off. Well, this took care of the right chamber but the left was still a very minute tight. I'll take the sizing die back for one last pass and that should clean this problem up. Will still use dedicated brass for each rifle.
Now, it appears, I will have my friend construct me one of his adjustable paper patch bullet moulds in .457-8 bore diameter to patch at 465-6 groove. With black this should do well. I am loading a duplex load to shoot tomorrow with 10 grains of 4759 and 90 of black with those soft lead .458 slugs just to see what happens with the undersized bullets bumping up. The Summer 2007 DGJ has an excellent article on the "progressive cut" Henry rifling and the measurements on the specimen measured for the article (a Henry 450 3 1/4) was .471 for groove. You can definitely feel the choke in these barrels. That's why it was necessary to measure 10 inches from the breach to get an accurate idea of the bore.
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Re: Alex Henry 450 3 1/4
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