Most feeding problems in an AR come from a faulty magazine. Try a different one and see what happens.
Then if the feeding issues continue, take a look at your feed ramps into the chamber to make sure there are no burrs.
Also, if you are using cheap commie steel cased ammo, throw all of it in the trash and try some real brass cased ammo. The cheap stuff will gum up your machine on the chop-chop!
ETA: I see you're using PMC Ammo, so that's good. It could be a break-in issue. Did you clean the gun good after you got it and lube everything well prior to you range trip?