I put my 308AR together the other day. Aero receiver set, BA barrel with mid length gas. Today I was looking through some forums and found that to make sure everything is lined up, put the bolt carrier in with no bolt and slide it forward and if there’s any resistance then something probably isn’t aligned. So I tried it out and felt resistance when the key came to the tube. I couldn’t get a good view to see where it was making contact. Took everything apart and was trying to find what I did wrong. I notice the barrel nut is slightly touching the gas tube. I looked down the end of the receiver and the gas tube seems to be coming in Perfectly straight. So on a whim i took off the gas tube and seen how it fit into the gas key when not on the rifle. It’s here I noticed that the tube didn’t slide right into the key. It was some resistance. There’s like a mushroom head on the tube that creates the resistance. Below is a picture of the little bit it goes in before resistance starts. So now I’m pretty sure that’s where I’m getting resistance. No the question is.. is that normal? Or should I get a new gas tube to install?