View Full Version : Why is my AC 556 jamming?

January 8, 2012, 07:39 PM
Why is my AC 556 jamming?

The gun is just back from Ruger for service. They "repaired bolt" which was explained to me on the phone as cleaning, deburring and replacing parts including the ejector or ejector spring (I think? I couldn't talk to the tech, so this was a translation of sorts.). It jammed about 10 rounds into firing clean and lubed. I fire only brass ammo. Various brands and types, (.223 and 5.56), only Ruger brand magazines.

Below are some images of what some of these jams look like. As you can see, this is on both sides as bullets feed from the magazine.

I am relatively new to firearms, but I am a bicycle mechanic by trade, so the function of small parts is something in which I am well versed. For the life of me I cannot reproduce this manually or see any obvious issues.

Any help is appreciated. I posted this a while ago, but my solution really did not fix the issue. http://thefiringline.com/forums/showthread.php?t=454908&highlight=ac+556+jam




January 8, 2012, 09:40 PM
I assume that's a spent casing on top in the pics.

It looks to me like the extractor isn't holding on to the case. It looks like its partially pulling it out then the case is released. The bolt travels to the rear, moves forward to grab another round and pushes it up into the spent case above causing the malfunction.

January 8, 2012, 10:00 PM
I agree with Sturm. I'd start by putting a drop of oil into the extractor area and wiggling it around a bit.

January 8, 2012, 10:04 PM
It is a spent case.

The thing is all those pieces in the extractor/ejector area move just fine. Like I said, Ruger just worked on it, and I before I cleaned it this evening, I checked to movement on all of those parts again. I am pretty serious about oiling parts...these had plenty of lube and were clean.

January 8, 2012, 10:28 PM
It's clearly some kind of an issue with the extractor letting go of the case too soon.I am pretty serious about oiling parts...Maybe too much oil on the extractor?

January 9, 2012, 12:43 AM
My guess is something is out of spec. The extractor claw could be worn or broken or the extractor spring could be worn or broken. It's also possible the bolt itself is damaged. But I would look at the bolt and extractor.

January 14, 2012, 09:31 PM
So I think I have this narrowed down to the extractor. Yes, it jams on semi-auto. It jams with both the 20 and 30 round original issue "LE/Gov't use only" magazines.

.223 cases ejected from an AR we shot today show "claw marks" from its extractor, and cases from my AC show only faint "shiny spots" where the extractor passed over the lip of the case, but no evidence of it solidly grabbing the case "groove".

If a new extractor, due sometime this week, doesn't fix this, anyone here interested in a deal on an AC 556 with accessories?

January 14, 2012, 10:24 PM
If a new extractor, due sometime this week, doesn't fix this, anyone here interested in a deal on an AC 556 with accessories?

If its a non-functioning price.:D

January 15, 2012, 12:31 AM
I'll give you $50 for that broken POS :D

January 15, 2012, 07:43 AM
The only problem I ever had with my Mini in 35 years was due to a bad extractor spring. It was doing what yours does. I hope you ordered the spring along with the extractor.

January 15, 2012, 11:56 AM
I ordered extractors, springs and plungers and I am going to replace all of these things. Glad to hear from a few sources that these have been an issue for others because that gives me hope that replacing these bits may fix the problem.

I'll keep the offers for purchase in mind guys!

January 16, 2012, 09:26 AM
Are you using a factory Ruger magazine? The feed lips on aftermarket mags tend to get out of spec and interfere with the movement of the bolt. I.e. the lips touch the bolt or permit the cartridges to bump the bottom of the bolt.

If you are using a factory ruger magazine, then it has to be the extractor or extractor spring. However, I will say this - the extractors on the AC556 are robust and don't usually break and they are not sensitive to too much/too little oil.

January 16, 2012, 03:59 PM
Are you using a factory Ruger magazine?

Various brands and types, (.223 and 5.56), only Ruger brand magazines.


January 16, 2012, 09:50 PM
Thanks PTK!

January 17, 2012, 12:14 PM
Is it really a 5.56 or is the chamber a .223, This will cause extraction issues. Ruger has very tight chambers in all of their rifles.

January 18, 2012, 12:10 AM
So I received and installed new extractor plunger and extractor today. Springs looked identical, so I am not sure which I put back in.

Extractor plungers, new on left:

New extractor:

Old extractor:

I lack the experience to tell for a fact that the old extractor and plunger are worn/damaged enough to cause issues, but they sure don't look healthy to me...we'll see this weekend.

Please let me know if you have thoughts on the condition of these components from the photos.


January 18, 2012, 12:46 AM
They look worn out to me, too. I'll be looking for your update this weekend.

January 18, 2012, 05:36 AM
I'd say you've fixed your problem. Keep us posted.

January 18, 2012, 05:01 PM
Oh HELL yes that looks like it was the issue. I'd be very surprised if that doesn't fix it for you. Glad you figured out the problem. :)

Also.... damn, that poor plunger. How many rounds did you put through this since the last replacement of the plunger and extractor? I looked, but I don't think you mentioned that yet.

January 18, 2012, 10:55 PM
I bought this last spring and maybe have 700-1000 rounds through it since then...no idea how many before that.

January 19, 2012, 08:37 AM
My AC556 is functioning properly, but I think I'm going to have to inspect these parts - plunger looks like it could have been the problem. It would be interesting to know exactly which part was causing the problem.

January 23, 2012, 10:06 AM
I think it's fixed!! I only shot 2 mags, but not a hitch!!

Thanks to everyone for your thoughts and insights.

January 23, 2012, 10:23 AM
Fantastic! :)

Now, my suggestion is to go get a spare plunger, spring, and extractor and tuck them away for the next time they need to be replaced. ;)

January 23, 2012, 09:42 PM
When I ordered, I ordered two of each.

January 24, 2012, 05:49 PM
Good call. I don't recall ever kicking myself for having extra replacement parts handy. :)

March 4, 2012, 11:26 PM
So I finally got a chance to shoot again today. After the gun got hot, I had several malfunctions identical to before the extractor swap.

Any thoughts?

Seemed to work fine after gun cooled again.