Took out my brand new DPMS just purchased from Walmart a few weeks ago. Before shooting it, I cleaned and properly lubricated it. I did replace the hand guard with a new tactical hand guard. Took it out to Pawnee National Grasslands today and it shot the first round fine. But it failed to eject the spent casing. It did not try to chamber the next round either. After getting home I noticed that the hand guard could have been pushed down another 1/4". So I loosened the hand guard and moved it down the 1/4" and re-tightened it. Therefore the gas tube was able to move down that 1/4" as well. Does it make sense that maybe the gas tube was not in the proper location for the gun to function properly? I fired 60 rounds through the gun, but I had to pull the handle back manually every time to eject the spent casing and insert the next round from the magazine. Sorry for the dumb question, I am still learning. Thank you.