Another newbee problem. I just finnished my first build and the gas tube has play were it passes through the upper. It also snags slightly on the key when the bolt closes. My issue m16A2 and old Colt Hbar bolts closed as smooth as butter and had no play in the gas tube. Is something missing?

The gas tube should have a small amount of play in it where it enters the upper receiver. It shouldn’t drag on the gas key though. Did you bend the gas tube trying to install it?

ETA: Separate the upper and lower. With the upper flipped upside down, slide the bolt and carrier back and forth observing how the gas tube enters the carrier key. The carrier key inner diameter is chamfered to aid in the gas tube aligning with the key during cycling. If the carrier key drags slightly on the gas tube but enters fine I would let it go. If the carrier key impacts the gas tube not allowing the two to mate you could try slightly bending the gas tube in the correct direction.

Sometimes a misaligned barrel nut will bind the gas tube to one side, but this doesn’t seem to be your problem since you say the gas tube has play.

The carrier key drags alittle too much on the gas tube for me. I am going to reajust the gas block position and if that does not work. I will pursuade the gas tube into better alignment with the key as a last resort. Thanks for the feedback.

thank God!  When I read "sloppy gas tube" I thought someone might have some serious personal problems with their rear-end!