Built an AR chambered in 7.62x39. Test fired it for the first time today, fires one round, ejects the brass cleanly, but doesn't chamber the next round. I have a rifle length gas tube on a 20" barrel. Most forums I've read recommend opening up the gas port in the barrel, I've also read a couple that recommend changes in the weight of the buffer or springs. Leaning towards opening up the gas port, does anyone here have real world experience and recommendations? What size should the gas port be? Haven't taken any thorough measurements, but the round end of a 1/8" drill bit will not fit. Using an ASC 30 round magazine. Everything works when I cycle it manually.