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Posted: 8/8/2011 9:49:52 PM EDT
So I am finally happy with my build, finished it about 2 months ago and have taken it out a few times. It was always hitting far right, I had good groups but they were always a couple inches off. I even bought laser bore sight that would always be far right of where I expected it to be. I was maybe one turn away from no more adjustment on my BUIS so I finally decided to do something about it. After looking at it over and over I decided "yup, that barrel is not sitting right". So I dismantled my DD Lite and took a look. My barrel nut was slightly cocked to the right, after taking it off I took my upper to work I'm a QC inspector in a CNC shop) and used our digital height gage and an indicator to probe the face that the barrel sits flush to. I zeroed out on the right side and took the indicator around the opening. I had .0035 difference. Just to back myself up i used some 1-2-3 blocks and squares and I could see light on the right side where the left was flush. Got out on of out table honing stones and started working down that left side, checking every couple strokes with my set up and the barrel its self.. when it looked pretty good I hand tightened the barrel nut. I had a couple coworkers take a look down the flat top and they said it looked straight (the same people said they could see it pointing right without me saying what to look for. Took her home and put everything back together. Didn't want to wait for a lapping tool with all the tools I have at my disposal.
 here is the face, you can see on what would be the right side where the stone just barely took anything off.
 here is a really crappy picture, wish i had taken a "before" pic, you could see how bad it was
 The finished rifle minus optics 
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Lapping can help some "out of square" uppers. Good job!!!
A great Q.C. practice is to always "qualify" the laser boresights before using them. I have seen some boresights where the laser is not parallel to its case. Turn the boresight on and chuck it in a drill press Place a piece of white copier or fax paper on the drill press table turn drill press on The boresight should "draw" a small red dot on the paper if it is running true Some boresights "draw' a red circle, indicating run-out of the unit and a VERY non-precision tool. |
| Lapping does help but it looks like a 16 inch M-4 cut barrel and your only going to be so close with that barrel its not a 20 inch target barrel... But yes lapping will get some precision back but how much I cant tell you its going to matter a whole of a lot......Nice stick.... |
| My lapping tool came in handy again the other day when I had a barrel nut that didn't want to line up. I lapped it a little more and everything went together fine. It sure beats knocking out the FSB pins on a brand new barrel and waiting for another barrel nut to show up that MIGHT work. |
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Quoted:
Lapping can help some "out of square" uppers. Good job!!! A great Q.C. practice is to always "qualify" the laser boresights before using them. I have seen some boresights where the laser is not parallel to its case. Turn the boresight on and chuck it in a drill press Place a piece of white copier or fax paper on the drill press table turn drill press on The boresight should "draw" a small red dot on the paper if it is running true Some boresights "draw' a red circle, indicating run-out of the unit and a VERY non-precision tool. I did chuck the bore sight in our lathe, it's true 
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you absolutly did the right thing... you said your groups were already good to go... just too far over to the right, and you didnt have room to dial it in with your irons... trueing the reciever face is definantly what i would have done..!!! sounds like you did a A+ job... soooo i would imagine it should striaghting things out... let us know how she shoots when you get a chance..
good luck... |
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