Freak barrels are available for Mags but expensive, and I think that Lvl 10 bolts have a problem with really small-bore barrels and inserts, if IIRC.
I wouldn't worry too much about bore matching - like Vintage said, as long as the detents can keep rollouts at bay, use whatever you want. I'm partial to All American barrels on anything I use, especially Mags... they've always seemed to work well for me.
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Originally Posted by HurtCow
And God turned to Gabriel and said: “I shall create a land called Canada of outstanding natural beauty, with majestic mountains soaring with eagles, sparkling lakes abundant with bass and trout, forests full of elk and moose, and rivers stocked with salmon. I shall make the land rich in oil so the inhabitants prosper and call them Canadians, and they shall be praised as the friendliest of all people.”
“But Lord,” asked Gabriel, “Is this not too generous to these Canadians?”
And God replied, “Just wait and see the neighbors I shall inflict upon them.”