[SigOhio]

So far, 35 members on here have discovered that the carrier in their newer build 556 rifle is hitting the receiver causing damage to the carrier. Please check to see if your rifle has the same issues so we can try to identify a problem batch.

This interference may be causing accuracy issues since it causes the carrier to bind just before coming all the way forward. But more importantly is that there is a defect causing damage that could compromise the longevity of a critical part that sees high stresses. I personally would like my 556 rifle to last me a long time, and I'm sure others here would as well.

Serial numbers with known carrier-to-receiver interference:

JS0228XX: Aaron (200 rounds) [mild]
JS023XXX: cufan99 (15 rounds) [mild]
JS0235XX: abrams_34 (800 rounds) [mild]
JS024XXX: dd0s (200 rounds) [moderate]
JS025XXX: bluecollarkid (300 rounds) [mild]
JS0250XX: fun2shoot (800-1000 rounds) [severe]
JS02500X: cheney (800 rounds) [moderate]
JS0255XX: jjksutton (120 rounds) [mild]
JS0259XX: tibim (800 rounds) [moderate]
JS0261XX: 762nato (50 rounds) [moderate]
JS0261XX: paxbnm (90 rounds) [mild]
JS0266XX: Parsley Charlie (200+ rounds) [mild]
JS0267XX: TwiztidKlownzTX (200 rounds) [mild]
JS027XXX: SigOhio (750-800 rounds) [severe]
JS0272XX: aaks38 (350 rounds) [severe]
JS0273XX: KB (cycled manually) [mild]
JS0277XX: 2Loud4You (200+ rounds) [mild]
JS028XXX: rioaguanegra (190 rounds) [mild]
JS028XXX: kylerudibaugh [mild]
JS0286XX: tangodown (hand cycled) [mild]
JS02963X: Mastoo (100 rounds) [moderate]
JS0300XX: Draco556 (1200 rounds) [mild]
JS0307XX: coffey (500 rounds) [Mild]
JS0309XX: hattaresguy (450 rounds) [mild]
JS0313XX: Sapper326 (360 rounds) [moderate]
JS0319XX: San Francisco SIG guy (600 rounds) [minor]
JS0320XX: TexRN (700 rounds) [Moderate]
JS032XXX: bravo5two (400 rounds) [moderate]
JS0332XX: anubismp (~700 rounds) [moderate]
JS034XXX: haiedras (125 rounds [mild]
JS0352XX: mlando (300 rounds) [Mild]
JS0378XX: bubbacop (200 rounds) [mild]
JT0004XX: Sam_SIG (200 rounds) [mild]
JT0012XX: bolt carrier (100 rounds) [moderate]
TP001XXX: EvilBlackGun (65 rounds) [mild]


Below is a list of serial numbers with NO wear or marking on their carrier at all, even though some have a quite high round count. Some have also indicated their upper receiver does not have the “humpâ€

 

[Longrifle]

You should also post a picture where it grinds against in the upper receiver. I remember seeing it in an earlier thread.

 

[SigOhio]

You should also post a picture where it grinds against in the upper receiver. I remember seeing it in an earlier thread.

Good idea, edited my original post.

 

[Longrifle]

I have a similar "hump" in my upper receiver, though not as high and don't have any grind marks. There is definitely machining quality control issue there. Mine is JS 0181XX (July 2008). The 3 SNs you posted are pretty close together, and like you said, may be a batch problem.

 

[Sapper326]

My Classic has those same wear marks on both the upper and the bolt carrier. My SN is JS0313XX made 4/22/2009. I really did not even notice it until reading this thread. I will try and get some pics but it looks very similar to the pics up above.

 

[SigOhio]

Updated the list in the first post. If you have this issue could you also comment to how many rounds you have fired, and how your accuracy is?

 

[Sapper326]

I have put roughly 360 rounds through the rifle.

 

[fun2shoot]

Accuracy not what I expected from my 556.

JS0250XX I have it as well. About 800-1000 rounds through my Classic.
Any word on Sig about this issue? I do not like the idea of the Sig smiths "quick fix" one bit.

 

[762nato]

Check Your 556 for wear/damage to carrier

I checked my two sigs compared carriers,commando-jso134xx-April 2008,its fine 400rds later,but the classic,JSO261XX-JAN.2009,50rds.fired.I can see where It's also starting to wear right on the corner just like yours.I need to shoot it more to see if it gets worse.But my commando does'nt have the slightest wear in those area's with eight times the ammo fired so far.Maybe your on to something here,My commando carrier is shaped alittle slimmer where they did the grinding on your carrier the radius is a little different,that's really hokey in my opinion how they did the grinding to cut corners .If any of you guys have access to different models,old/new,could you please compare the carriers to see if theres any difference in width/thickness,ect.Thank You,

 

[Longrifle]

I wonder if this problem is inherent to the new style "classic" lower. None of the older (from last year and older) NATO Stanag style lowers seem to have this issue.

 

[762nato]

I'm not sure,It could possibly be the upper's out of spec,and or the carrier,but I seem to think the carrier is the culprit.The classic carrier is just alittle different than the commando carrier,less meat,and a little different radius on the carrier.If someone has the insturments to correctly measure these parts,that would tell us more about the different sizes and radiuses/angles of these carriers.You know the old verus's the new. That's maybe why there catching on the corner like they are.

 

[tktm]

I have seen similar stuff in other AK's. I would be more concerned if it were damaging the locking lugs, or the piston.

 

[SigOhio]

I have updated the original post again. Looks like we are up to 6 members with this issue now and we are seeing a trend with the serial numbers. Early builds seem to be problem free. If you have this damage, please also post a pic of your carrier as well. It will help document what we are finding. No word yet from Sig.

Also, please comment on what sort of accuracy you are getting out of the affected rifle.

I wonder if this problem is inherent to the new style "classic" lower. None of the older (from last year and older) NATO Stanag style lowers seem to have this issue.

My rifle is an ER with the M4 style buttstock, not a Classic. I can only think of 1 way the lower could affect this, and that is related to the "charging handle bind" threads we have seen here. When the carrier hits the hammer and binds as it is coming forward, that places an upward load on the carrier guide rails in the upper receiver. This could be causing some extra wear on both the carrier and the guide rails, causing a looser fit which leads to this interference. From looking at the bearing surface area of the carrier to guide rail fit, I'm not sure if the guide rails were designed to handle that sort of upward load.

I have seen similar stuff in other AK's. I would be more concerned if it were damaging the locking lugs, or the piston.

The affected area is where the piston rod applies loads to the carrier, it is indeed a high stress area and I am concerned over the longevity of the parts with the wear seen. If replacing the carrier with a new off-the-shelf part just starts this problem all over again, then I see that as product defect and an issue for long term reliability. Not too mention that my rifle shoots erratic groups, and that this interference appears to be mostly at fault since the ground off corner changed how the rifle performed.

 

[Sapper326]

How much different is the 556 upper from the 550/551 upper? I wounder if this is even an issue or not. I have not seen any adverse effects from the wear as I am still able to maintain 1.5" groups at 100 yrds (which is what I would expect from such a weapons platform). This could be normal wear that takes place with this type of a platform. Unfortunately I don't think there is many people who own a real 550/551 and shoot them a lot. If there is someone who has access to one maybe they could check to see if they see the wear.

 

[SigOhio]

How much different is the 556 upper from the 550/551 upper? I wounder if this is even an issue or not. I have not seen any adverse effects from the wear as I am still able to maintain 1.5" groups at 100 yrds (which is what I would expect from such a weapons platform). This could be normal wear that takes place with this type of a platform. Unfortunately I don't think there is many people who own a real 550/551 and shoot them a lot. If there is someone who has access to one maybe they could check to see if they see the wear.

I'm sure there are varying degrees of severity, as this seems to be related to manufacturing tolerances. If yours doesn't look very severe and you are getting good groups, then yours very well could have essentially worn itself in and is now no longer hitting. If that's the case, then I say just keep shooting it and keep an eye on things. If you could post some pics it would help.

Unfortunately mine appears to be pretty severe because it began hitting again even after having the corner ground off. I would have been very happy if my rifle shot consistant 1.5" 100 yard groups.

 

[ullie]

I have seen similar stuff in other AK's. I would be more concerned if it were damaging the locking lugs, or the piston.

...the pictures clearly show that the carrier is contacting the reciever...slamming into it where it "should not" be making contact...with enough force to scar the carrier... in time possibly fatiguing the reciever...which may lead to other issues...this is unacceptable and needs to be addressed by Sig...pretty much a no brainer...

 

[jjksutton]

I have the same issue...JS0255XX (26 Jan 09)

Only 120 rounds (although I did hand cycle it a few hundred times). I can see a wear mark in the same spot. We'll see if it gets worse. I am going to the range Sunday.

I shot 2" groups at 100 yds with it which is more than good for me. We'll see if it keeps up.

Also, I had some issues with binding for about the first 30 or so rounds then it cleared up. I figured it "fixed" itself once. I don't know if one thing has anything to do with the other though.

 

[2Loud4You]

JS 0277XX Feb 11 '09 birthdate.

I've hand cycled it probably 500+ times and put at least 200 - 300 rounds through it. It has a VERY faint nick there. I barely even saw it, I'll see how it looks after firing more rounds through it.

 

[tktm]

I have seen similar stuff in other AK's. I would be more concerned if it were damaging the locking lugs, or the piston.

...the pictures clearly show that the carrier is contacting the reciever...slamming into it where it "should not" be making contact...with enough force to scar the carrier... in time possibly fatiguing the reciever...which may lead to other issues...this is unacceptable and needs to be addressed by Sig...pretty much a no brainer...

what exactly do you expect to stop the forward momentum of the carrier if it is not allowed to impact the receiver? Like I said, this is typical of AK's.

 

[tktm]

The affected area is where the piston rod applies loads to the carrier, it is indeed a high stress area and I am concerned over the longevity of the parts with the wear seen.

The piston loads are applied to the bolt carrier at the charging handle. The problem area is forward of that location. I would be more concerned about a potential binding / feeding aspect. As I said, issues like this are common in AK's but I would expect better in a high end AK.