Re: How heavy?
Weight does make some, small, difference off a bipod. That being said, I shoot the exact same size groups off a bipod as a full tilt benchrest with my sporters. If I were building a carry gun, geared tword long range, I would want it on this side of 10 lbs. I'd recommend you get something in that weight range, and then put a few hundred rounds through it off a bipod (after researching bipod technique). I think you'll find after that your plenty steady/confidant.
As for ABS barrels, no experience myself, but search for 'thunder' if you haven't already.
Empirical results rule!