So I was looking at one recently and I noticed the fit between the upper and lower had a lot of wobble. I was really disappointed. I would rather pay a little more for quality and I was a bit shocked cause in the past S&W was making some good AR's.

Not unusual, even in higher end AR's. It has no effect on accuracy, as the upper is the important part. If the sights and barrel align properly, you should have an accurate rifle.

__________________
SFC, US Army, Retired

My M&P15A (3/4 years old) and my Colt LE6920 have quite a but of play in the upper/lower. Doesn't affect shootability. Google Accu wedge if you want to take the slop out.

__________________
Rod
M&P 22A, 40c, 15A, 15-22

My Sport has wobble. I'm casually looking into the o-ring at the front lug or whatever as a solution.

Completely normal on an ar. Drop in an accu wedge to tighten it up.

The fit between upper and lower does have a small affect on accuracy. It's only significant for the absolute best groups possible.

The question I have is how much play is "a lot" in your understanding? Since the term is a little ambiguous, we can't tell if it's out of spec or not. Any way you could tell us just how much play in inches? Was it 1/8" of movement? More? Less?

__________________
Freedom isn't free.

It's called tolerance stack. There's a good chance that the next AR to come off the line needed a mallet and punch to remove the take down pin.

FWIW. my most accurate AR is also has the most play. It's the only rifle I own that will repeatedly shoot honest 1/2" five shot groups off the bench.

Unless it's custom built to your exact specifications all ARs will have some movement/wobble. It's not supposed to be a tight fit. And most rifles that come as 2 halves will have that.

It's a battle rifle. Battle rifles rattle a bit. That's a good thing.

Had mine out last night, noticed with a mag full of ammo installed, little to no wobble due to the ammo taking up the slack.

Just got in a couple accu wedges to try on my M&P15A and Colt LE6920. Colt, according to the masses, is supposed to be the bomb, of all my AR's, the Colt has the most wobble, so I accept this as OK. Plus the M&P and Colt are my two best grouping rifles, so seems no issue. I also appreciate the ease of which they come apart.

__________________
Rod
M&P 22A, 40c, 15A, 15-22

Get the dealer to pull several out and choose the best fit. I did that with my MOE Mid and found one with a snug fit that made me happy. YMMV

The AR is designed to have a certain amount of play between the upper & lower. I don't recall what the maximum allowable limit is, but if I believe, it's generous.

Do not put Accu-Wedges, O rings or any other foreign objects in your lower that you do not want falling apart and finding their way into the FCG to cause malfunctions ranging from failures to fire to run aways

Interesting thought; Perhaps the one I own was that next one (its the first version with the Troy furniture and sights) and is ROCK SOLID with no magazine in place. Though after reading all the reply's I guess its no big deal.

I think I would try that ACCU-Wedge as long as their was no chance in it becoming dislodged; BUT first I would use the gun as is to see if I could just get used to it.

Perhaps a bit of play is a good thing.

Is this wobble creating any issues for you?

I may look at a sport as a back up, does yours have those M4 cuts in the feed ramp?

My Colt has some wobble and functions fine. That being said I used like it was designed to...as a battle rifle. Meaning I don't sit at a bench and try for the smallest possible groups

I have taken up some of the play with aluminum looking tape.
I have placed some on the top edges of the lower receiver to take up the slop between the upper and lower. I don't remember testing with it. The accuwedge does make the fit tighter and it can be trimmed on the bottom to get the best fit on your gun. I think I have one in one of mine but I don't remember doing tests with it either. It is made of a rubber like material so under recoil it will flex. I do know that the choice of ammunition makes a huge difference, probably more than the tightness of receivers.
Given the choice I would rather have a fit that has the least amount of play. In my opinion having a sloppy fit does not aid in reliability or make the rifle function better in any way. Some lower receivers have a screw built in near the grip tang. The tip of the screw pushes up on the bottom of the upper receiver pin lug. If adjusted just right some say it removes some of the play which makes sense to me but I don't have any receivers that have that feature.

After reading about s.s. 0.005" AR-15 Pivot Pin / Take-Down Pin Shims I am thinking its a manufacturing problem related to any number of issues, such as worn out tooling, jigs, CNC wear and a failure with QA not forcing the CNC programmers to adjust to better programming practices. I also feel that any slop in a gun like this would wear out even quicker and have to be replaced sooner.

This actually stopped me from buying my second S&W AR until I look at some others to see first hand.

No real performance issues, just personal ocd/annoyance issues. It's the side to side play that I feel whenever I pick up the thing.
I keep mine very simple, iron sights and a few furniture upgrades (for the same reason, actually, wobble in the stock parts).

To me the upper/lower receiver wobble is a lot less annoying than loose/wobbliness in the 6 position adjustable stocks. Recently put on a magpul fixed carbine and the stock feels solid.

I build my own AR's using Mil Spec uppers and lowers and play between the upper and lower is completely normal. It also has NO measurable effect on accuracy and I can state that as an absolute FACT.

Because my precision AR was built using a Shilen Match Barrel in 223 Wylde (not the least bit cheap) using a Gibbz Arms Side Charging Upper (also not cheap), and a Gibbz Arms Handguard (a premium level price). Note, the fit between the barrel extension and upper was as ideal as can be achieved with it being a somewhat snug to start and requiring a light tap with a rubber mallet to seat, that is something that can be critical for accuracy. I also love the method Gibbz uses to mount the handguard and as a result only use Gibbz handguards in spite of them being a bit pricey.

As for the accuracy of this rifle, on a good day I've shot consecutive 3 shot groups spanning less than 3/10 inch at 100 yards. I've also found that due to aging eyesight my Sighting Error can vary from perhaps around 0.06 inch up to 0.19 inch at 100 yards, because on my more average days I'll shoot around 1/2. I've also had so many doubles in one bullet hole with this rifle I've lost count, last weekend I had two stickers that showed only 3 bullet strikes for 5 rounds fired.

Of course we dont know exectly how much wobble it actualy had but with typical wobble it wouldn't wear any faster. These are not race competition guns. And wobble or looser tolerance is not a bad thing. Obviously I'm not talking about 1/2 inch gaps here but some space between parts is perfectly fine. People swap uppers and lowers constantly to switch calibers and a lot of them run their rifles hard. If this was an issue it would have been brought up long ago

Like I said earlier, my Colt has some slight wobble. I can't tell you how many rounds I have through it. Cases upon cases of ammo and I bought it used. In its previous life it was a Pa state police SWAT/SRT rifle

Wobble is normal on an AR style rifle. It doesn't affect function or accuracy. I would not put any thing like tape or Accu-wedge on mine.

I had an FN Herstal M16A2 issued to me in basic training. The finish was completely worn off of it and the thing was sloppy as hell between the lower and the upper. The thing was a straight shooter, just looked like hell.