AR-15 FTF

[E-120]

I have a new to me Daniel Defense upper receiver that is having FTF issues. I was shooting a M-4 profile 16" Upper with Tula 223 ammo. Problem was about one shot per round in the beginning of range session and about one out of 3 by the end of the day. I used a C-products mag as well as a Magpul, and the bolt was lightly lubed.
I would shoot the rifle and occasionally the follow up shot would be a click. No round in chamber. A few times the bolt slid forward and bound on the next round in the mag.
I am thinking the the rifle may be short stroking.
Checked bolt and its supports its weight so I doubt the rings are bad.
Gun did not appear to be dirty, however since the problem worsened I am thinking debris may have been blocking the gas system.
TIA,
E-120
BTW, I switched to my Yugo AK and finished up a fun day at the range.

[ChrisTKHarris]

Have you tried some 5.56 XM193 to see if it is still short stroking? At first my DD M4 Carbine was having a similar issue with PMC Bronze .223, but after a few hiccups early on it hasn't malfunctioned since.

[E-120]

I will go to the range in 2 days and figured I would use some Federal. I did read about using mil spec ammo for the smaller gas port. Will try some better ammo if this is a common early hiccup. Thanks!