I built a 257 AI on a Czech Mauser running an F34 contour A&B. It was finished in June of 2008 and I've logged about 1100 rounds on it. While it is a bit heavy for me, it shoots lights out with multiple loads.
It loves the 75 gr VMax, 90 gr Sierra GKHP, and 100 gr Interlocks & Speer HPs. I mean like consistent clover leaves!
Yesterday I took it out to rezero it after having the barreled receiver parkerized and a new stock put on and had one hole 3-5 shot groups with those first three bullets.
Fantastic. Say what you want about these barrels, I've loved mine. Amazing what $90 can buy!
