I never used a BarSto, so I cant comment there, but I did have a LWD 40-9 for my Glock 31, and it worked flawlessly from the first round. I actually had more rounds of 9mm through the gun than I did 357SIG.
All I ever did, was drop the barrel in, and used my 17 mags. Everything else in the gun was stock. I have 17's, so there was no need to rely on the 31 set up that way, but from my experience with it, I wouldnt have had an issue using it.
I think if you vet the gun with the replacement, you probably wont have any problems. If you did have any issues, I would probably pass, or at least think pretty hard on it.