It's always a possibility that your upper & lower just don't play nice together.
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It's always a possibility that your upper & lower just don't play nice together.
I know upper/lower fit has little to do with proper function and accuracy but my best issued rifle had a good amount of play and the one that consistently gave me problems locked up with no rattle. Also echoing the previous post do not put anything in your lower, I've seen a guy suprise burst fire, almost lose control of his rifle, then get kicked off the line and handed paperwork when the range masters found accuwedge in his lower.
I hate the accu wedge and earplug methods. I don't like placing shit in my lower and they never do a good job anyway. The o-ring method is far superior IMO. Just stick a small rubber o-ring around the front takedown lug. Tightens better and more even than an accu wedge.
FACTS:
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The upper and lower receivers of Armalite self-loading rifles, and all other similar rifles
based on the AR-10 or AR-15 design, are held together by two pins. Unlike rifles that
are cammed or screwed together and can be tightened, the pins allow for slight
movement between the receivers.
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It is possible to selectively fit pins and receivers, or to custom ream the pin holes while
the receivers are held together, so that movement is minimized. Doing so reduces the
interchangeability of the receivers, and normal wear results in looseness over time
anyway. Armalite uses the reaming process on its National Match M-15 rifles.
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It is also possible to reduce movement by inserting materials such as paper, rubber, or
epoxy somewhere between the receivers and creating a tight fit or bind. Many
commercial customers use a common rubbery device claimed to improve accuracy, and
the Army Marksmanship Unit often uses a bit of epoxy. The AMU Armorers advise that
this procedure doesn’t improve accuracy, butit makes the shooter feel more confident
about their rifle.
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The AMU Armorers are correct. Formal testing conducted at Rodman Laboratories in
the 1970s verified that accuracy wasn’t affected by normal receiver tolerances. The fact
is that the bullet exits the bore before movement of the receivers produces a measurable
effect.
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Modern manufacturing processes are unable toproduce to dimensions that both allow full
interchangeability AND prevent all movement in all cases.
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Armalite’s rifles, except for some of the National Match rifles referred to above, are
produced to military standards of interchangeability to allow full interchange of
components. Tolerances have been deliberately tightened to reduce the movement
between the receivers, but remain open enough to assure interchangeability. Armalite
gets a close fit between the receivers, but normal forging and machining variations may
result in a small amount of play between the receivers or slight side to side receiver
mismatch. This is not a manufacturing defect and has no effect on accuracy.
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CONCLUSION:
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Armalite rifles are produced to tighter-than-normal tolerances. Receivers will normally
exhibit a certain amount of looseness. Thisis normal and will not affect accuracy.
Shooters may reduce the movementby insertion of a small amount of material between
the receivers to improve the feel of the rifle, but it won’t improve accuracy.
I used some hot glue in the area of the rear lug.
I lubed the area well and the rear lug (pin included). This is to keep the glue from glueing the receivers together.
This being done, i put just enough stuff there it would fill around the lug but not too much.
The result was a very tight fit. After about 3 mags (not firing fast) and a half dozen openings , it loosened up enough to allow for normal disassembly again.
I have Armalite National Match (oversized) pivot and take-down pins in a Colt and BCM. Completely removed the slop between receivers, but Armalite stopped selling them about a year ago.
In other rifles, I had a competent gunsmith drill and tap the receiver and use a nylon-tipped set-screw under the rear lug. IMO, the best method.
Personally, I don't like slop, but to each his own. While slop does not affect accuracy, neither does removing the slop.
I also have a set of 2A billet receivers that lock together like a bank vault.
IT'S ALIVE!!!
Put a stake in it.