Hey Folks.
I have built 100+ AR's over the last 10 yrs and for the first time built an M4 Carbine using a .223 Wylde barrel for my sons first AR. He reported back that he was out shooting it to do initial sight in, and started with several brands of .223 factory ammo and reports it shot flawlessly with tight moa groupings out to 100 yds.
He then broke out a 200 rd battle pack of M855 NATO 5.56 and says it turned into a single shot. Said it would chamber rounds just fine, no use of foreward assist, and it would fire the round but would not eject it. Switched back to .223 rds and again shot and cycled flawlessly.
Since this is my first Wylde barrel, I am stumped.
head spacing was spot on, so I am stumped. He lives a couple hundred miles away, so I am unable to help, I.e., change bolts/carriers, etc., but my understanding of the Wylde this should not be the issue if it's cycling .223 ammo flawlessly.
Any help would be greatly appreciated. I'm a 5.56 guy, but thought the Wylde would suit him better for using various .223 loads for accuracy when varmint hunting

Who's m855 was it? Sometimes foreign surplus gets sold on the civilian market for a reason. I purchased a case of Portegeus m193 ball in the 1980's that was loaded way too hot.

Who made the barrel? The cheapest budget barrels have had more issues than the ones costing $200+.

I am not a fan of the Wylde chamber.  I had the same issue with 2 different ar's that had Wylde chambers.  Milspec has enough slop spec'ed into them they eat everything.

Mine would fail to eject steel case ammo.

I am not a fan of the Wylde chamber.  I had the same issue with 2 different ar's that had Wylde chambers.  Milspec has enough slop spec'ed into them they eat everything.

The most probable cause is he may have some thick cases in the battle pack.  Hard to say without knowing the case manufacturers.  With the steel case it did not have time to retract fully before the extractor tried to remove it.  If your son is shooting some cases with thick walls it MIGHT BE that he is cycling too fast for those in particular, and they are not given that .000003 sec to fully retract.  Moving up to an h2 buffer might help.

.223 Wylde, CLE and Noveske Mod 0 are all better chamber options IMO than 5.56mm. 5.56mm has only one thing going for it, it works OK when really hot and pretty dirty.

Ammo all LC. This is the ONLY AR I've built that wouldnt eat EVERYTHING, including wolf steel in full auto or several hundreds rounds in an hour.
This is why I'm so puzzled and disappointed. I've read so many raves about how much  better the Wylde is when wanting improved accuracy for long range, although I've never been disappointed in any 5.56 ive built.
Barrel was bought through a supplier I've used for years, so not sure of brand. Just stamped .223 Wylde and unfortunately never paid attention to makers stamp outside chamber.
I guess I will just have to take a look at it first hand, it is his first AR. I always clean mine before firing, told him to do that (trying to get him used to stripping/cleaning), maybe its something that simple. Just hope its not a standard .223 stamped Wylde, I told him no more 5.56 until I take a look at it.
Thanks for the replies!

I have a new Ballistics Advantage Premium, 18" Wylde barrel and it 100% eats LC, GECO and IMI NATO in 55 gr., 62 gr. and 77 gr. just like my 10.5"/556 and 16"/556 units.  They also all perform similarly with any quality 223 pressure ammunition I have fed it.  I do not purchase nor shoot any of the low quality ammunition.  My guesses would be a bad batch of LC ammunition (doubtful) or a gas system issue of some type (probably) which could even be the gas port size drilled in the barrel, along with any other associated part of the gas system.