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Not a direct answer to your question about Mountain Air specifically but.....
I've spent time with 50+ airgun barrels at this point, I'd bet around 90% of those are Lothar's, and a large number of that in the sub20 fpe range that I think fits your intended size.
LWs generally seem to fit the bell curve of distribution that applies to so much of our existence. Ie... Most of them will be pretty decent. A few of them will be absolute crap. A few of them will be exceptional.
Polishing and/or lapping, as well as care on the crown, can definitely shift a barrel up, or down, the spectrum of performance.