Easiest way to eliminate the movement or “wiggle” between your upper and high-self lower receiver. I used an O-ring of .75" in dia., .1875" thick. Works great, feels solid. So far o-ring has lived up to repeat compressions with no damage. NOTE: I would like to retract this statement, as others posting to this thread have stated this suggestion is not a good idea.
You won’t feel the same way when some or all of that o-ring ends up in your fire control group…
I speak from experience as I have found a piece of rubber in a fire control group during a 3 gun match.
The guy’s response was “well, I put that in there to take out the slack between the receivers, but it was pinched in place so there’s no way it could just slide out”
When it slides under the trigger, your trigger STOPS working.
I hope your picture shows a brand new lower, because it sure has not been shot much if at all from looking at the buffer face.
Here’s a hint.
If the wobble was bad, it wouldn’t be there! 
If you don’t like the wiggle (I don’t either) use an Accuwedge, it doesn’t make the rifle more accurate it just makes the wiggle stop. JP makes a two piece rear takedown screw that does the same thing but requires tools to take your AR apart, which is why I don’t use one.
Ill get an accu-wedge…Thanks for the advise.
And, yes my LMT is new, haven’t fired this one yet.
Go to Lowe’s, HD or any good hardware store and buy some #7 o-rings.
Remove your upper from the lower and slide this o-ring over the front pivot of the upper.
Reattach upper and lower and all slack/wiggle should be gone.
Best of all if/when the o-ring fails it’ll be on the outside where it can’t mess with your tigger group.
the accu-wedge has no place on a serious fighting rifle that you want to depend on.
Why would that be?
Not to be confused with an armchair commando but I’ve fired a few rounds with one in my old Colt (and a few more) without any problems. In fact with the takedown pin locking it in place, it’s hard for me to imagine what might happen. Just curious.
Any time you place something inside your reciever that is not permanently attached, you take your chances.
I’ve seen one work loose and prevent a bolt from being able to be pulled back.
get over the little wriggle and concentrate on shooting and you will forget about the wriggle.
Actually, half of the o-ring ends up in your trigger and the other half falls off the outside.
I have actually SEEN this happen as well.
The carrier/bolt must have grabbed the piece of o-ring and taken it back to the FCG.
+1
They break up with use.
When a piece breaks off, it ends up in the FCG.
Also, they cause wear on the receiver and upper where the pin slides through.
After years and years of using one, you will find that the receiver has even MORE rattle when you remove it.
It’s sorta like Armor-All.
Once you start, you can’t stop or you end up worse off than when you started.
I had an accuwedge end up in my FCG at a EAG class in may:eek: . It did not bind up the hammer/trigger at the time(opened up the carbine to get out a blown primer that was stuck in the barrel extension) but surely would have given some time. I would like to think that I did not close the receiver with it loose but it is the most likely way it happened. After that I removed all of the accuwedges from my carbines and have learned to live with the little bit of wiggle.
Not really sure how this can happen as the o-ring is outside of the weapon from the beginning. When the upper and lower are closed there isn’t room for the o-ring to go inside of the upper.
I would have never thunk it.
I only have a Colt with a Diamaco upper left that uses one, guess I’ll remove it and see how bad the “wiggle” is. My other 2 are fine without one but seems like that Diamaco upper was on the small end of spec and the Colt lower was on the large end.
I don’t know how it happened either.
All I know is that after I removed the piece of o-ring from under the trigger and showed it to the owner, he said “that’s where the rest of that o-ring went…”
Turns out that the front part fell off earlier. :rolleyes:
all my uppers/lowers have some ‘wiggle’ to them - some are tighter than others. however, i only notice the play when i’m not shooting the rifle. i cannot recall ever noticing it when i’m actually shooting, since i’m always putting tension on the upper (either by supporting it or pulling back on a vertical grip), so it’s never been an issue to worry about when it counts. YMMV.
I would like to thank everyone for their input!
yeah, great thread.
That’s funny. That’s exactly what my circle of AR15 buddies told me when I inquired about the “play” between the upper & lower. And it’s true – shoot it enough and you won’t even notice it;) . Good info here!
The more I shoot the more I notice (like time slowing down, brass leaving the ejection port, the push of the stock into my shoulder, the smell of the powder, the rise and fall of the sights etc). When you do it enough you’ll notice it too, it’s like your mind is watching your body perform a well rehearsed play all by itself without thought. It’s awareness (aka Zen)…too deep for many.
“The right shot at the right moment does not come because you do
not let go of yourself. You do not wait for fulfillment, but
brace yourself for failure. So long as that is so, you have no
choice but to call forth something yourself that ought to happen
independently of you, and so long as you call it forth your hand
will not open in the right way–like the hand of a child.”
–Kyudo Master Kenzo Awa to Eugen Herrigel in Zen in the Art of Archery.