If going to custom actions then do yourself a favor and contact John Pierce at Pierce Engineering in Michigan, he makes actions to house anything from 223 to my 400 Warlord beast and up to the 50 BMG and larger ELR wildcats
he makes actions in chrome moly steel, stainless steel & titanium as well, if looking for a lightweight build
his shop is currently building us three actions for my moose hunting buddies that will be chambered in my wildcat the 300 Razor and we've had him build us complete guns before
Pierce can sell you an action for your smith to build on or he can build you the complete rifle
call him.. John Pierce is very approachable and easy to communicate with, fantastic gentleman
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Pierce Engineering