i’ve toyed with the idea of using a tiny bit of JB weld to fill in the gap on a mashed receiver index pin slot, but haven’t come across any fucked up receivers since the idea hit me. i can’t really recommend doing that, as i don’t know how industrious you are, but there it is all the same.
The 10,000 dollar question is, has this upper ever been zeroed??
If no, then you might have a bigger problem.
C4
As stated before, I removed the barrel nut and checked the index pin. It was fine. There was not enough play between the pin and the receiver slot to correct the amount of cant. Grant’s idea of using a BFH gave me pause as this didn’t seem like the logical thing to do as there was nothing that could give without breaking (i.e. index pin, taper pins, etc.).
It’s apparent that the FSB was installed canted at the factory.
Everything at this point is pristine and has not been damaged in any way. I will contact Steve at Adco about installng a new FSB.
Thanks for your comments.
Yes, I zero’ed it at the range today at 25 yards. As stated before, it took moving the rear sight completely to the left to zero it.
Yikes! You know next to nothing about building uppers!
ADCO cannot install a new FSB because the holes are already drilled into the barrel. The holes in the FSB are drilled AS they are drilling the holes in the barrel!!
Who made your upper? ADCO?
C4
LOL no. Was the upper ever zero’d prior to you installing the rail?
C4
ADCO usually does quality work, based on reputation alone.
If it was their mistake, I’m sure they will rectify it.
send it to me… i’ll fix the mother fucker. {does bad job of hiding the angle-grinder behind his back}
it’s a brand new 6920… ADCO didn’t do it.
if there’s no play between the index pin and the receiver index pin slot, put some on the right side and twist the FSB counter clockwise while tightening he barrel nut.
its either that or returning to Colt.
or having someone else do exactly what i just described.
or send it to me, and i’ll try my JB Weld idea.
If it is a Colt, then it was more than likely GTG. Once you removed the FSB, colt is not going to take the gun back.
So my guess is that the taper pins were not re-installed to their correct depth and or it just needs a nudge (with a hammer).
I bet that I could have this problem fixed in less time than it took me to post in this thread.
C4
Yes, I do know that the FSB and taper pins are dilled as a unit and installed together. Your idea to bang on the unit with a large hammer makes one question your knowledge.
Thanks for everyone’s opinions.
No, this was not an Adco upper. I had mentioned sending it to Steve earlier for repair. The unit is a DPMS.
I suggest that you NEVER watch how FN, Colt, LMT, BCM, etc install barrels and align FSB’s. In fact, look up the TV show where they went into FN and showed them making m16A2’s. They had a barrel being held at both end while spinning. The worker would then hit the barrel with a hammer in the center to straighten it out. 
The only person you should be questioning is you and your inability to install a FSB correctly. In the future, do not do any more builds as you will just cost yourself time and effort.
C4
I can believe that you got a canted FSB out of DPMS. The problem is that you never checked zero before removing the FSB. This would be classified as a mistake.
There are not too many options left open to you other then attempting to send the barrel back, filling the holes in and re-drilling a NEW FSB.
If it comes to this, you should think about cutting your losses and buying a quality barrel (as labor, shipping and the cost of a new FSB will make this DPMS barrel expensive).
C4
With the taper pins fully pressed into position, hitting the FSB with a large hammer can do nothing other than:
a) Shear the indexing pins
b) Deform the receiver
The manufacturing processes you mention above are using mallets to align the FSB BEFORE the taper pins are fully driven in.
This is a very imformative forum and it’s unfortunate that you feel the need to make negative comments unlike so many others here who provide relevant and accurate information. Rather than fuel the need for some to post more unproductive rhetoric, I will pursue my options elsewhere.
The pin will not shear off as it is steel and the receiver is Alum. You CAN impact the receiver notch IF you hit the FSB over and over and over again with a 5LBS sledge hammer. This is not what anyone is telling you to do.
If your windage adjustment on your rear sight is no more than 21 clicks from center, then it is technically “in spec.” So that mean that that the FSB only need to be adjusted a few hairs. One or two strikes will correct this problem (assuming that the FSB was installed straight in the first place). Since this is a DPMS, all bets are off.
Commonly, people believe that the taper pins are fully in, but are not. Just being 1/10 short will change the FSB’s angle (remember we only need for it to move a little bit).
One of the reasons why this forum is so “informative” is because I share my knowledge. I am telling you everything you need to know, but you are choosing to not accept it.
Your “options” are to sell the upper, install a low profile GB or let someone that knows what they are doing build your uppers.
Please let us know, how your “options” work out.
C4
Two of the most knowledgeable people on these forums are giving you free advice and options to fix your problem. You know Grant or bkb0000 could have said just send it to them and then sent you a bill. I haven’t been around here near as long as some people but I think its safe for me to say that you might want to check your attitude a bit.
Hell, I would have fixed it for FREE if he paid shipping.
C4
duuuude! back off a bit, OK? in old-time language, if you come to drink at the well, do not despair of the man who tells you your rope it too short to lower your bucket.
in other words, don’t jack with the man who gives you good advice, even if it’s not want you want to hear. in this case, Grant has probably built more AR’s than you’ve even seen.
there’s a reason AR 'smiths are called gun plumbers…
It’s fixed. Removed barrel, clamped and indicated TDC in relation to indexing pin. Indicated taper pin cuts in barrel (relative to tapen pin angle). Cuts were indeed not correct in relation to index pin. Installed and clamped FSB in correct position on barrel. Re-drilled and reamed for oversized taper pins (made them here at shop). Pressed in pins. Center of FSB site pin now indicates perfectly with barrel index pin.
The barrel and FSB were not properly aligned at the factory. No amount of pounding with a hammer was going to correct that.
I agree to disagree with the “Experts” on this one…
Glad you got it fixed. 
For the record I wouldn’t have been able to help you fix it but when asking people’s advice over the interwebs, pictures are definitely worth a 1000 words and may have eliminated some of the back and forth in this thread. A couple of car forums taught me that long ago.