At the range yesterday, shooting my .223 AR I had multiple incidents of the action cycling after firing, expended round was extracted, and ejected, and a fresh round loaded from the magazine, but the action was not completely cycled, resulting in the hammer not being cocked. The poor operator had to manually cycle the action, ejecting an unfired round, to make the next shot. I have not had this problem with this rifle in the past (built in 2010).

Ammo was Remington, boxes marked "55 GR. MC L223R3" this ammo has functioned acceptably in this rifle in the past, but dates from when the rifle was built.

What might be the issue? Not enough gas? Weak buffer spring? Buffer too light/heavy? Gas system needs cleaning? The cleaning will happen in any case, but what else should I be looking for?

Thanks in advance for any advice.

This message has been edited. Last edited by: architect,

Assuming that nothing has changed on the gun and it had been cleaned before taking it out to the range? Weak buffer spring wouldn’t prevent the hammer from cocking. If you’ve shot the same ammo before and haven’t changed buffer weights, that’s not the problem either. The AR gas tube (assuming that it’s a DI gun) is pretty much self cleaning.

Were the bolt and carrier properly lubed?

Based on your description, I’d check the gas system: gas block and gas key are tight, plus no other obvious problems such as the gas tube being blocked due to misguided attempts to clean it. Then make sure the bolt carrier is properly lubricated and there is nothing going on with the buffer and action spring.

I suspect that your disconnector spring is weak and is not locking the hammer to the rear quickly enough when the gun is cycling by gas pressure.

Your hammer is following your carrier back forward. When you hand cycle it, the disconnector spring has a lot more time to do it's job. Also, when you hand cycle it, the trigger isn't pulled. It is possible that your disconnector is actually broken and it isn't the spring at all, and when you cycle the action by hand the hammer is stopping on the sear and not when caught by the disconnector.



A heavier buffer might be enough of a band-aid to slow the carrier down. Or perhaps the rifle has a gas port that is too large and that is the reason for the excessive carrier velocity.



How many rounds through the gun and what was the source of your lower parts kit? I had a buddy who had a rifle doing the same thing with some no-name parts kit he found online. The springs were junk. Swapped him out with a good disconnector spring and he was back in business.


Three things I would check:

disconnector spring
disconnector
buffer/action spring


The fact that the rifle was working properly suggests to me that a spring is getting tired or your disconnector is broken. You have sufficient gas to pick up a new round.

It is a DI gun, gas system is not wiggling. I do not recall lubing the BCG in recent memory, probably dry as a bone.

I am a little confused about some of the comments, is it generally a bad idea to try to clean the gas tube and/or key? What are those long pipe cleaner doo-hickeys for?

A quick examination of the BCG showed that the grease on the rails had dried to the point where it was almost tacky, also, the bolt itself was a little sticky sliding in and out of the carrier. Hopefully, I will be able to get to the range within a week or two and verify that cleaning/lubing has cured the issue. I will report back if this is the case.

Just for my edification, several of the respondents above referenced "proper lubrication," this means a light coating of Teflon-based grease ala TW25 on those parts of the BCG that touch the upper receiver body, right? What else is implied by "properly lubricated?"

architect, based on my experience with ARs, I'm guessing you've got it fixed now.

And no, I don't clean the gas tube, never have since I started shooting M16s in 1967.

quote:

Originally posted by architect:
What are those long pipe cleaner doo-hickeys for?

To take money from the ignorant.

I bought a bunch of those extended pipe cleaners long ago when I was ignorant and now just cut them into shorter lengths for the things I actually use them for.

In my experience the most common reason for AR functioning failures is lack of proper lubrication on the bolt and carrier. When I used TW-25B, I smeared a visible amount on the four bearing surfaces of the carrier, and on the outside of the bolt where it contacts the inside of the bolt carrier. I now use Lucas gun oil in those same areas and again, it’s a sufficient amount to be seen and felt. One guide is that the lube should be enough for a fingerprint to be left in it when touched.

The lubricant doesn’t need to be, and shouldn’t be, so much that it’s running off or being blown back in the shooter’s face, but it really is vital.

ARs do like to be run wet for sure.

quote:

Originally posted by Flash-LB:
ARs do like to be run wet for sure.

Yep. More often than not, my experience has shown 99 percent of DI ARs problems are traced back to improper lube or lack of lube.

Pick any of the viscous lubes like SLIP or Lucas, and apply it. A lot of it. To me, I know the gun is lubed right when it slings a puff of smoke out of the ejection port on the first round or two.

If you lube guns, put them away, and leave them for a long time, you need to make sure that you use a lube that doesn’t break down and gum up over time. Also, it’s more than lubing just the rails on the outside of carrier where it contacts the inside of the upper. I usually also put some oil on the cam pin, a drop in the gas key, a very light coating on the inside of the carrier, and usually a drop or two of oil in the two gas vent holes in the side of the carrier. As others have noted, ARs prefer to be run wet more than dry.

There's got to be a way to adapt a Scottoiler VSystem to AR-15's.

This message has been edited. Last edited by: RichardC,

i don't use grease. I like CLP or hoppes oil

if its lubed enough to cycle the next round isn't it lubed enough to cock the hammer? I haven't actually looked in detail but I would be surprised if you have to actually go past the point of being able to strip the next round to cock the hammer. So I suspect the hammer is following and that is pretty much a trigger parts issue.
But willing to be proved wrong as always.

Clean and lube your gun. If it was maintained and lubricated I bet it works... and then this post and the ones like it never need to be posted.

You said the bolt carrier was bone dry and the grease tacky and dried up. In case you were not aware, the AR15 platform is THE gun in the industry that needs lubricated. It is one of the only guns I know of that needs what I would call massive amounts of lubrication and lots of it.... to include frequent re-lubrication every 300 rounds. When you take the AR15 rifle out of the safe, the first thing you should do is pop the carrier group out and lubricate the rails on it. Every time you pull it out before your shoot it. These guns needs lots of lubricant , way more than any other gun. You can’t over lubricate them, don’t be stingy with the lube.

For what it’s worth, I’ve owned a metric ass load of these rifles and have regularly put 10,000 rounds or more down range in them per year in normal times. These rifles just run and run and run perfectly fine, no jams, as long as they are WELL lubricated.

As some guy around here once said, get some damn grease on your gun.

quote:

Originally posted by hrcjon:
So I suspect the hammer is following and that is pretty much a trigger parts issue.

The more I think about it, the more I believe you’re right in light of the details provided—but that assumes they’re correct and there wasn’t some confusion about what happened. In checking an AR just now, the hammer cocks when the bolt carrier is moved only about half of its full travel distance which would be necessary for proper ejection and chambering of a new round. In addition to being cleaned and lubed properly, the hammer and disconnector should definitely be inspected. That was actually my first thought here, but then I got lured down the lubrication and cleaning rabbit hole. Plus, I can’t think of why manually cycling the bolt would cock the hammer, but firing the gun with full ejection and chambering would not. Does the shock of firing cause something to slip/bounce out of engagement that manual cycling doesn’t?

The hammer and trigger springs are directional on the AR make sure both of these are not in upside down. After that trigger group parts may need to be replaced. If you have another trigger group set, try swapping them out to see if the problem goes away.

Regarding “proper lubrication”, after a boarding (salt water wash down) we would flush the rifle with fresh water, blow out any water with compressed air, dry, then literally dunk all the parts in a 50 cal can of break free. And spray the rest of the rifle until break free ran off the weapon, re-assemble, and stand it in a corner on a rag until it quit dripping oil....they always worked after that process....

Nowadays, I just remove the rear take down pin, pivot the upper half up and spray the innards with oil...the BCG is usually slopping wi5 oil. Gun always works...if there is too much oil on it- it will sling it off with the first or second round...

quote:

Originally posted by architect:
...I had multiple incidents of the action....not completely cycled...

Your BCG is gummed up and probably dirty. It's dry. It doesn't move smoothly.

This must be rectified first. Clean the entire BCG and the insides of the upper. Then lube everything with a quality oil.

I bet your trigger assembly is loaded with carbon, grit, and old lube. Clean it, then apply a very light lube with oil. And check your springs.

Once all this is accomplished, shoot again and see what happens. I've never seen an AR fail to cycle due to being too clean or too properly lubricated. ARs repeatedly fail to cycle reliably for being dirty and dry as a bone.

Sounds like your hammer is following which can lead to it going auto eventually.

Check your disconnector geometry (be sure its not worn to the point where it doesn't catch) and disconnector spring (its still getting the disconnector forward during the FIRING cycle), check your hammer and trigger springs to be sure they are installed properly. If you cant tell then I'd put another disco and spring in.

You haven't done a polish or anything on the parts? Does the rifle have a lot of rounds through it? If its a home build, I'd check the tolerances to make sure all the parts are engaging properly.

I had the same issue recently and the rear trigger pin that goes through the disconnector was galled and did not allow the disconnector to move freely. It acted as though the spring was weak.
Truth in posting:
Advised to check disconnector by others.