Posted: 12/30/2011 3:34:35 PM EDT
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I was fairly impressed with my first PSA and ordered a second. Both seem to shoot great for me and have not had one hiccup.
But the first one is bothering me a bit about the sight settings. I have both a scope and the Magpul BUS sight on the rifle. Both are adjusted way to one side. Here is a picture of the rear sight zeroed at 100 meters. 
Do I need to disassemble the upper and square the upper to the barrel? Or is the barrel torqued too tight? Thanks! |
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That's funny, mine is a little to the left. not as far as yours.
It came out of the magpul package that way, i slapped it on, and what do you know, it shot dead on, so i never bothered to adjust it. it took me about 20 rounds to sight in the eotech and zero rounds for the back up sights. 
sorry, kinda dusty. i had the same issue on a pistol, sight came from the factory (new in box) with the rear sight adjusted right. it shot fine so i didn't bother it. mine is a gen1. thinking about moving my troy sight over from my m&p. |
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Quoted:
I had an upper that did the same thing. Almost all the way to the left with the BUIS. When I called the maker of the sight, he told me that is it zeros, it's fine. If it doesn't, it is the upper rail out of spec. It's caused by the differences between the upper receiver notch and barrel pin, not the rail being in or out of spec... The problem is the FSB is canted, normally to the left due to tightening of the barrel nut. To correct the FSB canting you'll need the obvious AR build tools like a vice, action block, and barrel wrench. You remove the barrel, and if, for example your FSB is canted left you basically use a small file on the side of the receiver notch to allow the barrel pin to move more right/upright, remove material slowly, keep eyeballing the vertical alignment and you'll be surprised how close you can get the FSB to perfect... You'll then need to tighten up the receiver notch, you take a small punch and hammer and slowly peen down the loose side/left side as in this example, to fill the area and keep the pin aligned... go slow, it won't take much to do it, the threads next to the pin will only have to slightly flatten.... Reassemble upper and enjoy! I started learning how to build AR's years ago for this reason, so I wouldn't need to depend on luck or shipping things back to have things properly done. 15-20 some odd clicks might be considered in 'spec', but it's not to me... The 2 PSA kits received in early November did exhibit FSB canting, one at 13 clicks and the other at 23 clicks left at 50 yards. I removed the barrels and adjusted the upper receiver notches, on the second range trip both of the PSA's sighted in 1 click right at 50 yards... |