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 said:You should also post a picture where it grinds against in the upper receiver. I remember seeing it in an earlier thread.
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.Longrifle said: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.
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.tktm said:I have seen similar stuff in other AK's. I would be more concerned if it were damaging the locking lugs, or the piston.
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.Sapper326 said: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.
...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...tktm said:I have seen similar stuff in other AK's. I would be more concerned if it were damaging the locking lugs, or the piston.
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.ullie said:...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...tktm said: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 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.SigOhio said: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.