I have an ar-15 flat top that will not fully cycle. sometimes it will not fully eject a spent casing and the rest of the time it will cycle but not feed the next round. i have had the gas block replaced. it helped but still does not work properly. running the charge handleit works flawless. its like having a bolt action ar-15. tried several different types of ammo but so far it has never worked like a semi-auto. ant input would be greatly appreciated. thanks

It sounds as if it is short cycling. Not driving the bolt back far enough or fast enough. They are not usually picky about ammo, but I'd make sure to try some 50-60 grain PMC or other pseudo-military ball round (rather than a super-velocity varmint round.)

See if someone will let you shoot your upper on their lower. It will at least rule out all the recoil buffer components as the suspect parts if it still fails.

If you can't try it on another lower, take the buffer components out of yours and check for binding, etc,

After you've ruled out the obvious things, I'd start to suspect the gas port in the barrel or the gas tube itself being partially blocked. Take the handguards off and do a visual to ensure the tube is not crimped or cracked somewhere.

The only time I've seen an M-16 short cycle was on a "shortie" upper. It turned out the gas burst was coming too soon and was too short also. The easy fix was to effectively lengthen the barrel by putting on a solid "flash suppressor". I suspect the proper fix would have been a larger gas port feeding a larger diameter tube for a short section under the hand guard to store more gas energy.

I have a friend who is quite an expert amateur with the M-16/AR-15, but it is very hard to work on them long distance.

I would go to a local NRA match and ask around. Someone will help or tell you who to take it to. Go early, before the sign-ups start. After that things get rushed.

Don

I've seen loose gas keys (the part bolted to the bolt) leak and cause short stroking. As others suggested, check for binding and plugged/leaking gas path.

Bullshooter, A guy next to me at the Ben Avery Range was suffering from a similar problem. He cleaned his rifle barrel twice while at the bench but nothing helped. A soft spoken old fella checked out the rifle and came back over with a chamber brush and some type of solvent. It seems that the AR guy had fired some type of laquered steel cased 223 foreign ammo and got the gun hot. The laquer had stuck to the chamber walls and the fired rounds were sticking. Hand chambered and unfired rounds hand ejected with ease. The older fella spun the brush in the chamber for a few minutes and put the gun back together. No failures to eject or feed after that. I talked to him a while on break and he said some of the laquered rounds will build up a sticky residue in the chamber. He told me not to use them, stick with brass. It made sense but never using the stuff I just took his word for it. Hope this helps. Good luck.

Excellent advice above. For more on the lacquered ammo problem, check the ammo section of this site:

www.olyarms.com

I believe that this applies to all Russian-made steel cased ammo, like Wolf.

BTW, Bullshooter, where do you shoot? Perhaps, Tacoma Sportsman's Club? I noticed that you live in Puyallup. Would like to invite you to Black Diamond sometime. Drop me an E-mail.

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Happiness is a 200 yard bughole.

I haven't had any problems with the steel ammo, (wolf or barnuel) but of course I don't heat my rifle up enough to melt lacquer either

I did have problems in my AR15 with the "Gazelle" box south african PMP. After 50 rounds or so the bolt face would be completely brass covered and the rounds would no longer reliably eject or chamber except by hand.

If the previous posters good advice fails, Try AR15.com Everything you can ever want regarding AR's and similar weapons. Try the Forums there.
FN