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Discussion Starter · #1 ·
i'm waiting to hear back from SIG today, but i've had a potentially major setback on my SBR'd 556 classic...

after the test fire, i stripped the gun down again, cleaned it down, and prepped it for refinish. as i was taping it up, i felt something move "funny"...

after prodding around a bit i noticed that the rail inside the receiver that the bolt carrier rides on, on the ejection port side, has nothing holding it to the receiver from the magwell step-down forward. it seems to have moved down, and away from the receiver wall in the area where it is not attached to anything...

i'm trying to find out it that area of the rail is supposed to be spot welded to the receiver wall or not. i would think it should.

anyhow, there is a small burr rolled up on the adjacent surface of the trunion where the carrier is banging into that edge as opposed to just sliding from the rail right on to it. it appears to me that this has been going to since day one, i just hadn't noticed it until now.

if anyone has a chance, please check your sig's upper and see if yours is similar to mine.

if this is broken or otherwise incorrect, i'll be on my own for a fix. being a form 1 gun, especially one that has had as much work as mine, sig won't touch this thing with a 10' poll (not that i blame them).
 

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Discussion Starter · #2 ·
here is a picture of the section i am talking about. the arrows show that area where the rail isn't attached to anything.




[/img]
 

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Mine looks the same I think. The first picture is trying the same shot you took (for some reason it is upside down) then I turned the receiver to get a better angle at the light.



It looks to me like the stamped top of the receiver is a U channel over the rails


The only thing I see holding the rails to the receiver is these spot welds.


I hope my pictures help you compare the two. You have a sweet set up in the making. It would really be ashame if there is a problem after all your work. Good luck. David
 

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Discussion Starter · #4 ·
dwhitehorne said:
Mine looks the same I think. The first picture is trying the same shot you took (for some reason it is upside down) then I turned the receiver to get a better angle at the light.

*snip*
The only thing I see holding the rails to the receiver is these spot welds.


I hope my pictures help you compare the two. You have a sweet set up in the making. It would really be ashame if there is a problem after all your work. Good luck. David
i'm not worried about the gap caused by the radius on the underside of the rail and the receiver. my gun doesn't have those spot welds...

if you put your finger on the front of the rail (close to where it butts up against the trunion where the left-hand arrow is on my picture), you can bend it up and down. it's totally free from the receiver from the magwell stepdown up to the trunion.
 

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Discussion Starter · #5 ·
small update:

i had a chance to talk to sig. i was told that what i was seeing is "completely normal". i can only assume i wasn't explaining my issue well enough, because i looked at a half-dozen 556's at lunch and every single one of them has a weld to hold that part of the rail to the receiver.

it appears that mine either a) broke free, or b) never had it.

i'm going to mill a couple holes this afternoon and plug weld the rail. probably tig it to keep the heat down... :x
 

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bullyforyou said:
i'm trying to find out it that area of the rail is supposed to be spot welded to the receiver wall or not. i would think it should.
......there should be a minimum of three welds attaching the rails to the reciever on each side of the reciever...one in the rear directly above the take down pin...one in the center of the upper above the hammer pin...and the one in front directly below the "bolt handle catch axle" when the BCG is in it's foward position...and a corresponding weld on the left side of the reciever..the rails should not be free to flex or move...



.
 

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Discussion Starter · #7 ·
ullie said:
bullyforyou said:
i'm trying to find out it that area of the rail is supposed to be spot welded to the receiver wall or not. i would think it should.
......there should be a minimum of three welds attaching the rails to the reciever on each side of the reciever...one in the rear directly above the take down pin...one in the center of the upper above the hammer pin...and the one in front directly below the "bolt handle catch axle" when the BCG is in it's foward position...and a corresponding weld on the left side of the reciever..the rails should not be free to flex or move...

.
yeah, mine doesn't have ANY visable plug welds anywhere on the gun. visable or not though, the front one is missing.
 

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What you're experiencing is now the norm in Sig rifles. This is the same issue that started my whole debacle with my new 556. It *should* be welded, but it isn't. My older Sig 556 does have the weld.

I sent it to Sig and got it back saying everything was fine, even when I have a correctly made rifle sitting in front of me.

It's crap like this that's made me swear off new Sigs.
 

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Discussion Starter · #9 ·
WayaX said:
What you're experiencing is now the norm in Sig rifles. This is the same issue that started my whole debacle with my new 556. It *should* be welded, but it isn't. My older Sig 556 does have the weld.

I sent it to Sig and got it back saying everything was fine, even when I have a correctly made rifle sitting in front of me.

It's crap like this that's made me swear off new Sigs.
yeah, the fact that my carrier is banging into the adjacent surface of the trunion instead of sliding on to it as it should, is proof enough that this is not "fine".

as an aside, the receiver itself also loses structure by not being welded there.
 
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