There's a Youtube video on how to perform the filing/stoning that's really good. Coincidentally, I watched it this morning.

I have a Bar-Sto barrel in a P229 in .357 Sig. Required a little bit of fitting but shoots like a tack driver. I have used there barrels in other non-Sig builds and have never had an issue. If they tell you it's in stock, it's in stock. If it's not, they'll usually have a projected time when they're going to do a run. I know Beretta barrels are usually a once a year endeavor.