It would be very close, depending on your elevation from 100yd zero with the new barrel - a 20MOA base would likely be necessary.
A 6.5mm 140gr A-Max @ 2820fps (26" velocity) requires roughly 41.75 MOA at 1200yd assuming 100yd zero, Litz G7 BC, 500' elevation and standard atmosphere (59F, 29.92 Hg).
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