Elininating slop in an AR with a high shelf lower?

[NWSharpshooter]

Accuwedge. Dear God, don't put epoxy in the lower.

High shelf. Accuwedge won't fit.

 

[lostgeorge75]

I use a little black rubber O-ring that is about 1/2" Home Depot sells for sink repair. Put it around the rear part of the upper receiver post that fits down in the lower that the pin goes into. Get the thinnest o-rings they sell. Works kinda like an Accu-wedge but much cheaper. The o-ring is squished between the upper and lower. Here's a sample but this o-ring was too thick. You can also put it on the front of the upper.

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[Clearance_Clarence]

I didn't say lower

 

[mtdawg169]

I bet you won't notice it being loose if you just shoot it!