Hi, I have several MK5 rifles and a couple of them are customs. I also have 3 Vanguards that have been re barreled. My 7mm Mashburn was built on a Vanguard in 300 Wby. This is the only Vanguard that has a 3.580 long mag box to handle the 300 round. A gun smith can open up a std mag Vanguard like Wby did by milling out the feed ramp and front of the mag well to fit the 300 box. The only real hassle with the Vanguards is the metric barrel threads, I had to wait a little longer for the gun smith to do the barrel set up. Good luck. Randy
