Play in Receivers

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pwrstrkd

New member
How much play should there be between the upper and low reciever. For example if an AR-15 is stood up with the stock on the ground and the barrel is rocked back and forth from the muzzle, should there be obvious wiggle and movement felt? At first thought it was the barrel :eek:
 
My Rock River has ZERO play between the upper and lower. I don't think it's typical to have play between the 2. If there is play, it's more than like due to a pin issue or pin hole issue...
 
Some play is indeed typical. Very few uppers and lowers fit with no wiggle, even from the same manufacturers. If it bothers you that much, you can put an Accu-wedge in it, but unless the slop is extremely excessive, it won't affect accuracy.
 
Play is pretty common. Some are worse than others. Some have none at all.

I have a Bushmaster that had a lot of slop. It took a home made accu wedge (the real one wasnt big enough) and an "O" ring on the front lug to get it to stop wiggling.

My M&P 15 has a little, my Colt and Armalites, none at all.
 
My DPMS doesnt have much, but my brothers DPMS did have a ton of wiggle. I say did because he couldnt get groups any smaller than 3" at 100 yards while I was getting 1" or less with the same model gun. I took his gun, cleaned it up, retightened/remounted everything, and I put gasket cork in the lower reciever under the back pin until you had to actually force the upper and lower together to push the pin through. It tightened his groups up ALOT, hes getting groups less than .75" at 100 yards now. I dont know if it was the cork or the cleaning but he never could get groups under 1.5" even when it was new.
 
I used to carry an m16a1 that you could probably fit a dime in between the receivers but on the zero range at 25 meters it could put 3 rounds in a hole so small you almost thought you missed the paper with the other two. and never had any reliability issues either. it's annoying but it's nothing to worry about.
 
It varies, but here's how mine breakdown.

Zero Play:
LaRue OBR

Very little play:
S&W M&P15 OR
S&W M&P15 MOE
Armalite AR-10

Some play but not bad:
Bushmaster
 
I recently put a Bushmaster receiver and a DPMS A3 flattop stainless barrel together. The fit was sloppy at best. It shot very well but I just didn’t like the rattling so I did what Technosavant suggested and put an Accu wedge in the lower. It’s now tight as a drum, in fact it’s actually hard to push the take down pin out of the lower without something to push with.
I really don’t think that it affected accuracy that much. But it was worth the 6$.
http://www.midwayusa.com/Search/#Accu-wedge____-_1-2-4_8-16-32
 
I'd like to have mine tight but can't say the wiggly ones shoot poorly either. I've got a couple that have to pounded with the palm to close and popped over the knee to open. On the other hand, they never get tighter with use so starting out snug is good.
 
After retiring from the Army and finding this forum, I was amazed the first time I read that people think there should be no play. Just hilarious to me. Your sighting system is 100% on the upper, so who cares what the lower is doing?
 
Your sighting system is 100% on the upper, so who cares what the lower is doing?
Click to expand...
If youre using the rifle in a "target" capacity, its very annoying, and I find it to be a distraction. Really, its just a distraction anyway, regardless the use.

I agree that from a mechanical stand point, it probably wouldnt make a difference (assuming the upper is fixed), but from a consistency stand point, I think it will, even if it were to be more mental than physical.

I wonder how many who shoot in competition have a "sloppy" gun? Im thinking not to many.
 
Wouldn't parallax affect iron-sights accuracy in a upper receiver that wobbles around?

My Daniel Defense had a lot of play in the receivers. Very annoying. I slapped an O-ring on the front takedown lug and got rid of the slop.
 
I can imagine it would be irritating to precision shooters, it just is not something I would worry about.

KChen - I have never heard parallax used in the context of anything other than a scope - can you elaborate?
 
500px-Parallax_Example.svg.png


At the most basic, parallax is an apparent displacement or difference in the apparent position of an object viewed along two different lines of sight. Make a circle with one hand and a front site post with another. Now move your head around. See how the front site post covers other things when your head moves?

That's basic parallax. I'd imagine receiver wobble would change the position of the irons with relative to the eye.
 
KChen986,

In your diagram you represent the iron sights as a single object. In fact, they are two objects that must be precisely aligned.

Geometry teaches us that there is only one straight line that goes through two points.

Proper sight alignment actually means that there are 3 objects aligned. The shooter's eye, the rear sight and the front sight. Combine that with what we know from geometry and it drives us to the conclusion that there can't be more than a single viewpoint through a single set of properly aligned iron sights.

If the shooter's eye isn't on the same line as the front and rear sights then the sights will appear to be misaligned to the shooter and he will have to move his eye or the gun to put the sights into alignment--eliminating any possibility of parallax at the same time.

While the sights are misaligned the shooter could experience parallax in terms of where the front sight is superimposed on the target, but once the sights are aligned to the shooter's view then there is no parallax because his eye is in proper alignment to view the sights without parallax. Parallax is, in one sense, a function of the viewer's misalignment with the objects being observed and iron sights force the shooter to put his eye in the proper position to eliminate any viewer misalignment. Iron sights, when properly aligned, can not suffer from parallax.

With the sights properly aligned the shooter's eye is also in line and all that remains is to adjust the gun and shooter position to get the front sight where it belongs on the target.

That said, sufficient play in the receiver could force the shooter to slightly adjust his eye/head position for each shot as the upper moves in relation to the stock cheekweld. That wouldn't be helpful to consistency which ultimately amounts to accuracy.
 
That said, sufficient play in the receiver could force the shooter to slightly adjust his eye/head position for each shot as the upper moves in relation to the stock cheekweld. That wouldn't be helpful to consistency which ultimately amounts to accuracy.
Click to expand...

Yes, but for that much wiggle to be present, the thing would have to be well beyond tolerance stacking to being well and truly out of spec.

The minor amount of play I've seen in most every AR I've handled is not going to be an issue unless you're doing competition at a rather high level, and in that case you'll have a rifle set up for that specific task. For combat accuracy, a set of in spec receivers is not going to wiggle to the point where you're missing your target.
 
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