With the Sig P320 the FCU is the numbered part Sig FCE. From there you can swap it into pretty much any configuration you want. But as others have pointed out, in a SHTF scenario you are better off with complete guns not parts for 6 guns and only being able to use one at a time.

Last edited by antelope_sniper; 12/20/21.

You didn't use logic or reason to get into this opinion, I cannot use logic or reason to get you out of it.

You cannot over estimate the unimportance of nearly everything. John Maxwell