Barrel manufacturer

http://www.barsto.com/

It means it is an after market barrel. However, they make aftermarket barrels for many guns, and many people replace their stock barrels with barsto barrel because sometimes they are considered more accurate than the stock barrel.

Expensive barrels, too. Well, guess I'll have to see if it is, in fact, more accurate. I know it was dirty as all get out.

Someone dropped some good money on a really good barrel. That's exactly what it means.