Ok so I built my first upper. It 20inch, so rifle length gas tube and a low profile gas block. I made the mistake of buying a cheap Chinese low profile block and realized none of the gas holes seem too line up just right. So I chucked that and bought a steel one from cobra tac. Everything lined up as it should. So I took it out and It fires the first shot just fine. It eject the shell and won't load next round. Tried different mags, same problem. The lower I put it on and BCG I know are in good operating condition as I have had em for years and never had a problem. Stripped upper was bought from aero. Rifle gas tube is Brownells. Barrel is a spinta precision. I began to disassemble this morning to look for the problem and I see a leak at the gas block. I will post pics. Your thoughts on what I should do next would be much appreciated.