Currently doing a 7mm Rem Mag build off a remington 700 LA. My stock is a bell and Carlson M40 stock for the LA rem foot print. Can I use bottom metal and the detachable magazine from a remington 338 lapua 700P? I think the mags length is 3.6. Is this bottom metal too long for my B&C stock? Will there need to be custom fitting for it to work?