I have a preban Colt AR15 Match HBAR that is marked on the lower receiver as Cal. 223 but it is also marked on the Barrel as 5.56mm. The box is no help either as it is a Blue Label Model 6601 & says .223 (5.56mm). it is also marked on the BBl as a 1/7 twist. Is there a definite answer, or am I worrying about a non issue?