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Posted: 9/3/2011 2:49:13 PM EDT
| Gents: M-16A1 kit builid shoots very tight groups but still two inches to right on 25 yard zero with rear sight full left. To cant front sight base to the right (move POI left) do I need to punch out the pins or gently use rubber mallet with barrel in vice? v/r W |
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First off, take a look at the center of the feed ramps on the barrel, and compare it to the front take down lug on the upper receiver to see if the entire barrel twisted in the upper socket when the barrel nut was sighted.
If the center of the feed ramps is canted with the FSB, then the Gods love you, and it's an easy fix. If the barrel feed ramp is centered on the front take down lug, but the FSB is canted, then you have a repairable problem, but will cost you some money. On the former with the entire barrel that has slipped in the upper receiver socket when the barrel nut was tightened, you can either reinstall the barrel to solve the problem, or if you want the gun shop fast way, remove the upper receiver from the rifle, lay the receiver on one leg with the barrel across your other leg, then using a non marring leather mallet, strike the FSB just above the barrel while only holding the upper receiver tight. The leather mallet force is will be enough to slip the entire barrel back to the needed correct index in the upper receiver barrel socket. On the later with the FSB and the barrel extension pin not on the same index, here you want to make sure that the center of the barrel feed ramps is centered on the front take down lug, then replace the FSB with a clamp on style instead. Trying to inlarge/redrill the taper pin channels to clean up the index is just going to be a nightmare. Also to note: if you can get the rifle sighted in, even having to take the rear sight dam near all the way to the side, you can slip the barrel/reinstall the barrel to correct the problem with the FSB and barrel extension pin slightly off each other. There is enough gap between the bolt lugs and barrel lugs to allow such and not causing binding problem of the two locking up/ unlocking from each other. 
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