Caused problems - JP Enterprises Supermatch Barrel With Headspaced Jp Enhanced Bolt, 6.5 Grendel

I ordered the barrel from JP Enterprises for a 6.5 Grendel build I was working on and had nothing but issues. I couldn't, for the life of me, get the rifle to cycle. I tried different buffer springs, different gas rings, 3 different gas blocks (2 of which were adjustable), a lighter bolt carrier, and every different bullet that was on the market, including hot handloads. None of those fixed the problem. Turns out the Gas port on the barrel was not drilled large enough (.075ish). This forced me to send the barrel to someone to drill the port out and since then I have not been able to get a group better than 2 MOA, again with every bullet on the market and handloads. Could possibly be an issue with how I put everything together, but I followed spec instructions in my building process and have put multiple other AR-15s together without issue. I can't recommend this.