Bismuth is not a cure-all when it comes to ring bulging.
I have first hand knowledge of a set of 12-ga. fluid steel barrels with M/F (.020/.035) chokes and 3" chambers that never had anything other than bismuth shot through them when the left barrel developed a ring bulge from shooting just 8 cartridges of 3" 1 3/8 oz. bismuth loads through them. It was explained that a phenomenon termed "momentum" caused the ring bulge -- too much of a load at too much speed through too small of an area.
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Wild Skies
Since 1951
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