As an owner of 1 of 500 original Costa Mesa AR-18s (serial range #1000-#1500) that Armalite sourced Apex match barrels for somewhere around 1962-1964 in order to make the market requirement for further Army and Marine testing, I can say that I know exactly what
@GeneT45 is saying... the real AR!
Is yours an Armalite (not many made- 3000 maybe) or a Sterling (widowmaker, 30k units imported to US) or a Japanese contract Howa (also 30k units imported)?