All I can tell you is that the 311284 was designed for rifles with wide lands, (i.e. the Krag), which is not your typical 21st century barrel. The nose is bore diameter and must ride on the lands or else it cocks sideways and shoots patterns. A very good design for the 2-groove Springfields, probably not for your Blackout. You ought to troll thru the Accurate Molds and NOE Mold catalogs to find something that has a groove-diameter nose and a short ogive.
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