To kind of pile on...I've been seriously contemplating the 7 Mashburn and the 28 Nosler. I have a push feed M70 7mag with a loose spot in the bore. It shoots OK but I thought it would be a fine candidate. I also have a very nice 300Win M700 BDL, but it shoots good and I'd hate to permanently modify it if going to 28 Nosler.
So if I've understood correctly, my pushfeed M70 shouldn't need any modification to go to Mashburn or 28Nos? I'm thinking about a 27-28" tube with Light Palma or slightly lighter profile. I have a heavy laminated target stock I'm going to trim down a bit that should soak up recoil without a brake on the barrel.
I think I'm leaning towards the 7 Mash but need to look into die and reamer availability. I haven't looked too deep yet, but kind of see it being a wash between the cheaper brass but more costly and rare dies and reamer of the 7 Mash versus $2 brass but fairly available 28 Nosler dies and reamer, especially as more of them are built. Forming brass doesn't scare me. I haven't worked much with belted cases, is anyone needing to use those collet dies that size that last little bit before the belt? That would be an additional cost unless I built one myself.
I would consider that nice one Safariman has for sale but I can't seem to connect with him...
