[ladams]

Can I build a 6.8 sbr with a lower that is marked 556 and do I have to have it remarked in the correct caliber,

 

[batman4706]

If the barrel is not marked so that it can be seen without removing anything, then you need the caliber along with you name, address, etc.

I have 2 300 blk SBR lowers built on multi frames and had them engraved with 300 blackout.

 

[ladams]

Thanks