Any of these barrels have the potential to be a great shooter. Stay away from the Shilen barrels sold by Brownell's. They used to be pretty good. Last four years I don't know what happened. The A & B barrels sold in Midway are a little variable in quality - some are real good. They look almost identical to Douglas through the bore scope. Maybe seconds? Probably as good as most factory barrels, and half the price of a Douglas.
Douglas barrels seem to have gotten a little better in the past five years. Very good value for the dollar. Rare to get a lemon.
Hart is always good. So is Lilja and Krieger. About the same price range. I still use more Kriegers than all others combined. They machine like butter. Quality is very consistent. And I like dealing with German boys from Wisconsin

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