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Discussion Starter · #1 ·
Hello, this is my first post and it saddens me that it has to be a complaint. I have several Ruger rifles and pistols. I love them all. But, my AR556 doesn't seem to like to feed the cartirdges into the chamber. What is happening is the bolt is not closing completely. Then the cartridge is stuck in the chamber. The rifle is new with less than 100 rounds through it. It has been cleaned, several times and oiled very well. I ran about 60 rounds of Magtech through it when I first got it. I came across a good deal on some Geco, so I bought along with some Armscor. I managed to get about 18 rounds of the Geco through it before things started to go wrong. Misfire with the cartridge stuck in the chamber. Once that was removed, I tried again, it fired but the next round got stuck without being fired. Got that out, switched to the Armscor. Can't even get the bolt to close with those. Cleaned the chamber and neck again, no issues there. So, I got my calipers out and started measuring the rounds. The magtech all consistently measure 9.41mm at the widest part of the body of the shell... All the others consistently measure 9.48-9.51mm at the same point. I got to looking at some specs online for those cartridges, and what I found is that the max dimensions of those cartridges are supposed to be 9.55mm. So, if my ammo is within spec, is it possible that my chamber ( neck) is too small?? I removed the upper and dropped one of the Geco rounds into the neck and noted how far it fell in on its own. Then I put a magtech round in there and noted how far it went on its own. The magtech went significantly further into the neck than the Geco with nothing other than its own weight. Nothing is more frustrating that a new gun you can't shoot!! BTW, after all the issues with the Geco and Armscor ammo, I went back to the Magtech and have no issues. :(
 

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It could be that the chamber was drilled slightly small, and the added expansion once hot is pushing it beyond the ability to cycle. Are the cases scratched at all from the clambering process? Either way, definitly call ruger, they'll make it right.
 

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Discussion Starter · #3 ·
Yes, the rounds are marked like the case had gone down the barrel. They have spiral marks all the way around them. Like they were spinning when trying to be loaded. It is not an issue only when hot. The Geco and Armscor rounds won't allow the bolt to close when cold!!!
 

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Are any of the bullets cocked to one side when you get them out of the chamber from being stuck? has the shoulder of the case of stuck bullet been altered?

Checked the barrel feed ramps in relation to the upper receiver feed ramps. Make sure the barrel feed ramps aren't sticking out past the upper receiver feed ramps, I.e. and edge for the bullet or case to catch on when sliding up the ramp.
 

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Discussion Starter · #5 ·
I got ahold of Ruger. Sending to them to mess with. Thanks for all the suggestions.
 

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sdxp787, I went through some "tight chamber" growing pains with my AR556 too. I got 100 rounds of Federal Independence ammo with my AR556 ... part of a gun show special. On the 4th round, I had a cartridge stick in the chamber where the bolt would not go into battery. I tried other cartridges and they chambered OK. When I got home, I measured the "stuck" cartridge and found it was a mere .001" larger than other cartridges that would chamber properly. I sorted through the remaining factory ammo and found one more "fat" cartridge.

When I reloaded for my AR556 and used the same Redding 223 Rem dies I had been using for the past 20 years for my Remington bolt action, I found none of the reloads would chamber. Soon after, I bought a RCBS "small base sizer die set" and my problems went away. I did some research and found there are 9 different popular chamber reamers that are use to final ream 223 Rem and/or 5.56x45 chambers at the factory .... each with their own unique set of measurements. Why? The standard 223 Rem cartridge and corresponding chamber is regulated by SAAMI so they are seldom a problem in a normal sporting rifle like a bolt action, however when you get into Mil-specs and NATO specs for ARs, you can find several different manufacturing specs. To add to the confusion, there is a "223 Wylde" chamber that is a hybrid between the civilian 223 Rem and the military 5.56. I don't know which spec Ruger uses but it has to be one with a tight head diameter.

No doubt, the cartridges you had problems with had slightly larger bases ... quite common. In fact tight chambers are quite common with ARs chambered for 5.56x45 NATO. When you combine these two attributes, the result is a stuck case, yet they will fit in a Wilson case gauge. If you look at the sales literature for small base dies (RCBS or Redding), it says that reloads may not chamber properly in AR chambers .... they sell a lot of these small base dies which proves this issue is not unique to Ruger AR556 rifles.

Here's a simple test jig I made out of a circular gap gage. The hole was drilled and honed until it was exactly the same as my AR556 chamber. I can now test all cartridges ... factory or reloads and find those with fat heads. The first photo shows a cartridge with a head that is just .001" too large. The second photo shows a cartridge with the proper sized head:




 

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Eye-Oh,
Good post. All my reloading gears is RCBS. Upon beginning to shoot DCM Service Rifle years ago the first thing I did was purchase the small base set. No issues ever.

I also use a Wison case gage but as you mentioned there are now many slightly different chamber sizes. The actual chamber test jig you made up is excellent.
 

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Found this earlier today while reading about the Wylde chamber

 

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crracer 712, An excellent reference that shows 8 of the 9 different chamber reamers. I believe the one missing is a Clymer Wylde ... similar but not exactly the same as JGS Wylde. There might even be more ... but these are the most common. If you look at the above chart at Dimension C ... Base Diameter, (not counting the exceptionally tight 223 Rem Match), you will see why some rifles may gag on some brands of ammo. There is as much as .0015" difference in base diameter. In my test jig pictures .... the cartridge base in the top picture is just .001" larger than the one in the bottom yet prevents the tapered case from chambering by at least 1/4". The hole measures at .3803". Point being ... it doesn't take much to for a cartridge to change from "go" to "no go".

You wouldn't think the solid brass case head would expand when fired .... but it does. Good case in point .... when I fired the Independence ammo detailed above, it chambered just fine (except the two rounds I noted). After I recovered the spent cases and cleaned them, none would fully chamber in my AR556. After resizing with my 223 Rem Redding sizer die, again none of the empty cases would fully chamber. After using the RCBS small base sizer die, all cases would chamber just fine .... proof that case heads expand when fired. When cartridges won't chamber .... as in the OP's original post. I guess you could blame the ammo or blame the gun but the best solution if you plan to shoot factory ammo is to have the chamber reamed slightly. I really like the 223 Rem Wylde specs .... virtually any commercial 223 Rem or military 5.56x45 ammo will chamber and the chamber will have a deep enough throat to accommodate any Mil-spec ammo. If you reload, the simplest solution is to buy a small base sizer die. BTW, the same thing happens in a 308 Win .... AKA 7.62x51 semi-auto rifle so small base dies may be just the ticket.
 

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Speaking of go, no go, to bad the OP doesn't have a set to try in his particular chamber. Shouldn't be an issue, but would be something 'neat' to check in a situation like this.
 

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Iowegan,
Here's a simple test jig I made out of a circular gap gage
That sounds like what American WWI Ace Eddie Rickenbacker did. They couldn't figure out why their machine guns jammed so much until he checked the diameter of their bullets. He then drilled a hole in a piece of metal and they checked each cartridge before they loaded them in the belts of their guns. It nearly stopped all jams.
 

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Sorry for bringing this back from the dead but I had this exact same problem w/ my rarely used AR556. I tried to shoot Armscor 223 rem ammo diameter (dimension C) ~ 0.3745" and consistently gets stuck. Some PMC ammo slightly thinner 0.3710" is fine. I cleaned the chamber w/ a copper wire brush and a bunch of degreaser/cleaner and the problem persists. Is there something wrong w/ my AR556 or the ammo? What do you guys suggest?
 

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Sorry for bringing this back from the dead but I had this exact same problem w/ my rarely used AR556. I tried to shoot Armscor 223 rem ammo diameter (dimension C) ~ 0.3745" and consistently gets stuck. Some PMC ammo slightly thinner 0.3710" is fine. I cleaned the chamber w/ a copper wire brush and a bunch of degreaser/cleaner and the problem persists. Is there something wrong w/ my AR556 or the ammo? What do you guys suggest?
As long as you don’t insist on shooting the Armscor ammo, no, there is nothing wrong. I’d shoot it a bunch, then maybe later try the Armscor again if you want. By that time, the chamber will be “broken in” (if there is such a thing), and the Armscor may work just fine.
 

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mediabox, If you go back and read this entire thread, you will see your issue is a combination of "fat" ammo and a tight chamber. You can fix the ammo issue by buying a different brand. You can fix the tight chamber issue by having the chamber reamed with a 223 Wylde finish reamer. Of course you can send the gun back to Ruger with a sample of your "bad" ammo ..... or you can buy a new barrel. No, the chamber is NOT going to break in so I'm afraid you are stuck with the problem unless you do one of the above.
 

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Iowegan, thanks for the fix options. I don't think changing ammo brands is a good solution. As you mentioned several of your Federal Independence ammo were "fat" as well causing random lockups. Do I need to bring my calipers with me when purchasing ammo and measure each bullet? Essentially I can't trust this gun to shoot a round unless I measure my ammo.

The C dimension for all the reamers above are 0.3779" and greater. The box of Armscor is ~ 0.3745" give or take a thousandths (I measured w/ two calipers). That means the Ruger barrel I have is improperly bored and not within spec. Yes I have already contacted Ruger, this is not right.
 
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