I have seen this issue before with the AA piston Middy upper and the VLTOR A-5 and you need to reduce the buffer weight to 3.8 oz's for solid function with 5.56/.223 factory brass pressure loads and down to a 3.0 oz's if shooting weaker steel cased.
Now another issue I have also seen on piston guns is bolt carrier tilt which can be exaggerated if the bolt receives to much up-ward pressure from magazine contact. This will cause the charging handle to feel as it is dragging during cycling but the real contact is the bolt trying to aligning its self into the buffer tube.
Look at your buffer tube and see if there is any abnormal wear occurring in the first few inches. If you find none then it maybe be just simple drag on the bolt from the magazine and to much weight in the buffer.
We are all inclined to judge ourselves by our ideals; others, by their acts.
Bookmarks