I just looked at our 2 SIGS and noticed that the upper receivers are designed differently in that area!

On one of them, that area the red arrow points to is raised just like the one in the photo, sticking up higher than the part of the receiver leading to it but on the other one, it is flush with the receiver!

Will try to post photos this weekend.

...the raised area you indicated with the red arrow next to the caming ramp needs to be "ground down" ...it serves no purpose...the trunion and reciever steel are harder than the steel that the carrier is made from...so that this raised area is cutting into the carrier... scaring it...

...the only area that the carrier should be impacting is the "raised area" of the trunion...this area will have the finish worn off from impacting the carrier face...and is located near the ejection port @ 11 o'clock...you can see it through the ejection port or while looking down the reciever channel with a light...likewise...you can see the resulting shadow on the carrier face...another wear area will be on the caming ramp made by the small and narrow bolt lug as it makes contact there...starting the bolt to rotate...

...this most probably is a result of machining error in which not enough metal was removed (as per the print specification) for that component...i suspect the only way to correct this is to replace the entire upper reciever since everything is already welded...or dremel it out...

So, do we need to call SIG again??? Is this something they need to address or something we need to pay a qualified gunsmith (in short supply around here) to do?

For what it's worth, before sending in my rifle the last time I went to the local gun shop and looked at 4 other brand new 556s. They all had the raised bump there, so either they were all defective, or that is how they are machined now. The carrier in all 4 fit in the rail much more tightly then in mine, and I could not feel the carrier hitting the bump while moving the charging handle forward like I could on mine.

Some pics of mine.

...it's not so much that they are defective...it just seams that the raised area is creating some tollerance issues in the sense that "in some rifles" the carrier is not clearing the raised area each and every time the weapon is fired...most probably due...for examply...to small differences in the placement of the rails in the upper reciever and small differences in the rail channel width along with the acceptable demensional differences in the carriers...that is...the location of the channel and ledge in which the rails glide relative to the carrier body for example...these are the shortfalls of the manufacturing process when interchangability of parts is required...and allowable tollerances are increased...sometimes tollerance stacking occures...

...i suspect that your carrier is not impacting the raised area each and every time you "fire" the rifle...since there is...and should be...a considerable amount of play in the system...however...in your case...there may be a little too much play...along with possibly one or more out of spec or improperly aligned components...

...unfortunately i don't have your 556 in hand to better determine the cause...and can only give you my opinion based on what you posted...

...Sig should have anticipated any possible issues as a result of any changes in their finish machining of this component..."if" in fact that is what occured here...and should realize that any demensional changes could affect the entire system... their engineering staff should be well aware of the "allowable" tollerances of the entire weapon...leaving "extra" metal in that area would require decreasing the tollerance limits of everything that has a mechanical relationship here...

JS019XXX - no wear or markings at all on the point in question. 5500 rounds through.

Mine is more faint than fun2shoot's. I honestly had to look REALLY hard to see anything. I plan to get to the range this weekend though so I'll see if more damage occurs.

I bet you shoot at United Sportsmen in Concord. My buddies and I go there a lot. Looks like you got yours shortly after me (JS 018XXX). Welcome to the bullet button club

if something is out of spec between the upper and the bolt carrier..

i hope it's the bolt carrier that's out of spec.

it would be a lot easier to replace.

...DELETED...

...tktm

...don't polute this tread by trying to start an arguement with SigOhio...notice i didn't say please...

I have this issue, it's not as profound as the photos, but I did notice SOME scarring. Is a little scarring normal?

That is more rounds fired then any others I have seen so far. This is a very good datapoint, thank you very much for sharing it.

Thank you for the pics, I have added 1 of them to the 1st post.

Here is how I decided to start classifying the amount of wear so we can try and see a trend with high or low round counts as well. If anybody has further suggestions/comments on this feel free to share them.

[Mild]: Shiny marks indicating some contact and/or light rubbing, not obvious without close inspection. No significant carrier material deformation. This fits the descriptions by Parsley Charlie, 2Loud4You, and a few others.

[Moderate]: Shiny marks + some small amounts of deformation of the carrier material/shape. I think this fits the pics shown by tibim.

[Severe]: Large amounts of material deformed and/or removed by this wear, extending the full length of the worn edge back to the radiused corner. See the pics by SigOhio and fun2shoot for reference.

I think if you have Mild wear and your rifle shoots good, just keep an eye on it and enjoy your rifle.
If you have Moderate or Severe wear, it's up to you on if you want to send it back or not.
From what we have seen so far I think Moderate wear will eventually progress into Severe wear with higher round counts, which could lead to longevity and accuracy issues (if you don't already have them).

Still no response from Sig regarding this issue.

If you could please post your serial # and round count I can add you to the list.

Per my last post, I think that "Mild" wear is probably ok as long as it does not progress. Anything more then that may be a concern, and you should keep your eye on it.

can you post PICs of your carrier and upper receiver?

i'd like to see if they're are any differences between yours and the others posted PICs.

thanks

EDIT - SECOND RECEIVER PHOTO ADDED

Here you go. I can change the angle and background light if needed. Looking at range log, this one has closer to 6,250 rounds through it. Going to put 1200 rounds through her this weekend at a training course so will take the same shots on Sunday night for comparison.


Upper receiver 1 - with a bright light shining down the receiver.


Upper receiver 2 - different focus point


Carrier

As per photo #5 with the red arrow indicating a newer design for the casting. My 0090xx and 0095xx have no such protruding bump. I can honestly say that i would not buy any of the new 556s that are outside of the first 11,000 produced. All of the AWB banter has surged the market to the point where the manufacturers are pumping out absolute shit. Sorry for anyone who has a post 11k. But it's a fact!

Does anyone know at what point (serial number wise) Sig switched from Swiss made internal parts to the home grown variety?

Serial number on mine is JS0076XX. I show no marks on the carrier or the receiver but I only have about 1000 rounds thru it.

An additional 120 rounds today, no noticeable further damage.

~1200 rounds no marks. SN: 187XX

JS0090XX, 2000+ rounds from Barnaul, Privi, Federal and Lake City shot through it. No wear what so ever and a tack driver!

I don't disagree with you, but for the record every 556 that was reported in this thread has a SN at 25000 or higher. They all appear to have been built in 2009.

JS O17xxx

No abnormal wear in indicated areas appx 500 rds.

Just under 1000 rounds through this weekend on JS019XXX - quick wipe with and oil soaked cloth and no difference from my photos above.

Depending on the outcome of SigOhio's repair(which should be completed soon), I think the rest of us that have this issue would do best to contact Sig as a group and let them know we would like this resolved.

I think we can conclude that this issue is an oversight by Sig engineers/machinists/QC as it has affected a definite range of rifles which were all built in 2009 and share very close serial numbers. They definitely changed something in the production of the 556 around the time these guns were produced which is causing them to all have wear in this area. It appears that people with rifles built before or after this time frame are just not experiencing these issues.

So I'm anxiously waiting to see what they do for SigOhio's rifle.

And anyone else with wear in this area please post up so we can expand our list of affected serial numbers.

yeah.. i agree with you.. hopefully SigOhio will have a good report for us.

what i'm afraid might/will happen is..

instead of machining down the part of the upper receiver that hitting or replacing the upper completely.. which i think is the correct thing to do.

SIG will just machine down the corner of the bolt carrier for clearence.. which is just putting a band-aid on the problem.

If you look at sigohio's 2nd picture there's no peening or wear on the second beveled edge.Then go to picture 3 after sig quick-fix,slight peening on 2nd beveled edge.Then picture 4 severe peening/wear on second belveled/leading edge where there was no wear before sig did the grinding.So no the grinding of the carrier is not helping matters just making things worse.I'm curious to see how they fix sigohio's 556 but I think they will just put a new upper on his,but if there are ton's more with this problem they will probably just start grinding the hump down inside the receiver if it has no ill affects on how the gun runs .I guess we shall see,

Thank you for posting these great photos. These clearly show that your upper receiver does not have the offending protrusion that mine does.

What's interesting is that several of the new 556's I checked out at the local store have an upper receiver with the bump that looks like mine on the inside, but the carrier fit much more tightly in the rails. I didn't check the serial number or the carrier for wear on those, but of course they hadn't been fired yet anyway. I'm guessing it's a combination of the bump in the receiver and/or a loose carrier fit in the guide rails that controls if you have this wear, and how severe it is.

Now word from Sig yet, I will call this afternoon if I haven't heard back by then.