Here's another view of the failed Sierra jacket - the jackets were not, as some would have us believe, the "cure". . . "peening" of the meplat is plainly visible. Popular belief is that Sierra jackets are "tougher" (perhaps slightly) and THICKER (absolutely NOT). Though both Sierra and J4 state that they use an alloy of 95% copper and 5% zink, the former are, in my experience, ALWAYS of a different coloration (comparatively "pink"), & ALWAYS of THINNER jacket wall construction. Since Sierra trims their jackets to length via a single point cut-off tool, the Sierras only "appear to be" thicker: the FULL cross-sectional area of the jacket wall is exposed. On the other hand, J4s are "pinch-trimmed" - the excess is stretched off - which creats a "knife" edge, thus the PERCEPTION of thinness. As a rule, comparable J4 jackets have invariably measured from 0.0005" to 0.001" THICKER than their Sierra counterparts: this amounts to, roughly, from 2.5 to 5%.
Does Sierra anneal their jackets? Subjectively, maybe - during point-up, they are invariably FEEL more malleable (softer). I have yet to encounter a Lot of Sierra jackets which featured less than 0.0003" TIR in the walls, while for J4s, this much run-out, while right at the upper [allowable] tolerance, is unusually "bad" - most J4s run at < 0.0002" TIR. Bottom-line: it was believed, by many, that the Sierra jackets would eliminate the bullets failures - NOT IN THIS BARREL, which is, at least, proving to be a good test platform.
However, via a pair of PacNor barrels, both chambered for the 6x47 LAPUA, by Mike Bigelow, Tom did, at Pierre, SD, win a 600 Yd. TWO Gun title, using "Moly Coated", Sierra jacketed, 109 Gr. BIB FB for the HG and "MC", J4 jacketd, 98 Gr. BIB FB during the LG - both, based upon roughly the same jacket length, shot quite well. More on "Moly-coating" later. RG