Make sure you line up the scribed lines perfectly on the gas port adjusting screw because the gas port holes are very small. I did find that both my svt-40's run great at the 1.3 gas setting seems to be the norm. If you open it too far open like the 1.7 setting the bolt carrier will slam into the rear of the receiver. I had one do that before i noticed it was too far open on firing one round. Bill