I am sure you are aware that there are different specs for go/no go/field for the 5.56 vs the 223.

I always use the mil-spec no go for 5.56 which off the top of my head is 1.4736.

I believe I have two rifles that will easily close on a 223 no go gauge that will not close on a 223 field gauge (1.4696) which is less than the 1.4736 limit for the 5.56. Both rifles function and shoot just fine.