I guess because all
FTE's from shitty steel cased ammo are from out of spec chambers.
To the OP, BCM is a very reputable company and any problems you may encounter with your rifle, be it your shitty choice of ammo or not, should be taken care of by them. That's just the type of company they are.
If you are going to spend the money on an outstanding company like BCM, why would you run shitty steel cased ammo through it? I know its "cheaper", but you get what you pay for, and ammo prices are coming down and still falling, $270/1K for quality brass ammo isn't that expensive. Just sayin'.