AR15 wobble, play, loose upper lower receivers
National Match Shim
.tightens AR15 wobble lower receiver, accuwedge
Tightens Receivers
Improves Handling
Helps Accuracy
Slows Wear
Overview...
The National Match Shim fits the recess next to the takedown pin lug and eliminates play without altering the original takedown pin configuration. The shim is surfaced gradually by hand until the takedown pin fits snug for target shooting or reduce thickness more for a pin that glides through perfectly aligned bores, either way the receivers will feel tight and right. Tools needed: caliper, screwdriver and pliers.
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Will the shim work in your rifle?
Visually verify the chamber is cleared. Open the receivers, remove the charge handle and bolt carrier group. If present remove the polymer AccuWedge. Lay a blade type .012" automotive feeler gauge across the lower receiver above the safety lever. Close and hold the receivers together firmly. If the takedown pin resists any when pushed or finds resistance passing through the receivers means the shim should work. If the pin passes through with no resistance means the shim may not work. Also check recess depth, it should be .090" deep.
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Remedies for receivers that gauge too loose...
Replace pivot and takedown pins measuring under .248" diameter. Upper and lower receiver pin bores should be close to .249" - .250" diameter. Pin bores slightly over .250" can be fitted with oversize pins available from JPRifles.com. The takedown pin lug bore in many upper receivers is an approximate .250" x .260" slot machined to align with various lower receivers, check for vertical wear.
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