308 Based Cartridge in AI Long Mag?

[lencomatt]

How does that work? Do I just get a 300WM mag and load the 308 in it or is there a special mag for it? I'm thinking about a Cadex Chassis from Drake and while I don't want a 338 Lupua now I might later and don't want to buy the stock twice, so i was thinking about just doing a 260 or 7/08 for now.