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Canted FSB repair on an AR-180

Abacab

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Normally I shoot my AR-180s with a scope but decided I should probably zero it for once. The rear flip aperture is set for 200/400 yards but unfortunately only have a 100 yard range.

Zeroed it at 100 yards but had to move the rear sight nearly to the end of travel on the left. Front sight block is canted to the right.

Asking around for opinions on how to fix this or if I should leave it alone.

On AKs we usually drilled for a larger pin size after straightening the block. The 180 uses tapered pins whereas the AK has straight. Could reream for the next size up.

Other suggestion has been to weld up the pin slots but I'm just a tad bit leery of welding on a barrel. A lot of opinions out there that it'll damage accuracy but had a hard time finding opinions from people who've done it.

Or I could just leave it alone. It's a nice example which makes it a shame they did such a trash job at Sterling.
 

yovinny

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Wait...something very wrong here..
If your front sight is tilted to the right, your rear sight should need be all the way to the far right, not to the far left..

Edited,,to correct for tiny keypads and fat fingers.. ;)
 
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tac-40

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Give the front sight a good whack to the left with a rubber or plastic mallet. If the front sight block moves, then you may need to re-drill the alignment pin holes for larger pins after checking to see if the barrel rotated. Also check your sight block gas port and tube are in alignment with the center of your upper receiver. This could also indicate you barrel is not properly installed (torqued).
 

Abacab

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Wait...something very wrong here..
If your front sight is tilted to the right, your rear sight should need be all the way to the far right, not to the far left..

Edited,,to correct for tiny keypads and fat fingers.. ;)
As I wrote my initial message, what you said occurred to me but I thought I was wrong and just went ahead and hit send.

You are, of course, entirely correct about where it should be if the sight is canted right. In the list of possible causes of my issue, I put the shooter as number one. I'm going to take it out and put it on paper (I was using a steel target before....) and rule out myself before wondering aloud if my rifle is screwed up. Not my finest effort so far.
 

Abacab

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Give the front sight a good whack to the left with a rubber or plastic mallet. If the front sight block moves, then you may need to re-drill the alignment pin holes for larger pins after checking to see if the barrel rotated. Also check your sight block gas port and tube are in alignment with the center of your upper receiver. This could also indicate you barrel is not properly installed (torqued).
I've never had a barrel off on one of these, just the gas assembly and front sight block. Is that how the barrel is installed on them?
 

tac-40

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IIRC. the barrel is threaded onto the upper receiver much like the FAL. Very early AR180s had a lock nut holding the barrel in place while the later ones had a shoulder cut into the barrel and was torqued up like the FAL. If your front sight block is canted to the right and still functions properly, it could mean the gas port and gas/sight block is properly positioned but the barrel is not threaded on correctly. When you say canted to the right, is this when you are looking from a normal firing position or looking down the muzzle towards the stock. Another thing to look at would be the bolt and chamber area to see if there is any abnormal wear in the locking lug of the bolt and chambers caused by misalignment (from the barrel not threaded on properly).
 

Abacab

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IIRC. the barrel is threaded onto the upper receiver much like the FAL. Very early AR180s had a lock nut holding the barrel in place while the later ones had a shoulder cut into the barrel and was torqued up like the FAL. If your front sight block is canted to the right and still functions properly, it could mean the gas port and gas/sight block is properly positioned but the barrel is not threaded on correctly. When you say canted to the right, is this when you are looking from a normal firing position or looking down the muzzle towards the stock. Another thing to look at would be the bolt and chamber area to see if there is any abnormal wear in the locking lug of the bolt and chambers caused by misalignment (from the barrel not threaded on properly).
Normal firing position. I have not had any function issues. Only issue I had was the pin that holds the dust cover to the receiver kept backing out when firing it. Had to take a thousandth or two off it to get it to seat properly.
 

tac-40

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Canted right looking from rear is an indication the barrel is not torqued properly if all other things are normal. But that doesn't follow this little ditty:

If it shoots to the right, the barrel is too tight. (you would see the sight block canted left)
If it shoots to the left, the barrel needs more heft. (you would see the sight block canted right)

So if your back sight is all the way to the left, that indicates it is shooting right which means the sight block should be canted left. So now I have no clue as to what is going on except the gas block could be installed improperly and needs drilling and new pins. Or your barrel could be bent, twisted, or otherwise damaged.

Can you remove the front sight or bend paper clip to run it through the gas port and see if it aligned correctly with the gas block ? Being off center could be the source of your cant.
 

yovinny

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Are there barrel flats on the chamber area of the 180,,,, or am I thinking of the AR70 ?
I cant remember,, havent been that deep in a 180 for decades..
 
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