The small case capacity of the .30M1 will not show much of an improvement with a barrel over 18", a couple hundred fps at best, maybe. I used two .30M1 barrels on my Contender frames (both 10") and found that they could take slightly higher than book loads safely - but the pressure is higher than SAAMI specs. You won't get much expansion from typical .308" bullets, although the V-Max 110s may work best.
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