i couldnt wait any longer so i picked up my mp x today. i notice that the upper and lower has a wobble between them is this normal? also some things kinda lead to me to beleive it isnt brand new, but the box was sealed with numbers matching box and gun. probably just weary i guess.

My 15 OR's upper and lower didn't fit as well as I wished when I got it. I trimmed down an accu-wedge to use in it and that took care of the problem. They say that not having a tight upper/lower interface doesn't affect accuracy, but I personally find it really annoying....just like the Magpul MOE hand guard that wobbled around. (it's at the bottom of the parts drawer)

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Stu

Slight wiggle between the upper and lower receiver is absolutely normal. The lower receiver has no impact on accuracy* and merely holds the trigger assembly and everything together. If it really bothers you, you can consider an Accuwedge or a modified "accurizing" rear takedown pin. These only help your rifle "feel" better and remove the wiggle, again they have no impact on function or accuracy.

* The only time sloppy upper and lower fitment can lead to accuracy problems is if the wiggle is so bad, that the upper receiver and it's attached sights/scope/optic will move around as you have the weapon shouldered. This would have to be a very significant degree of wobble though and is not present on most badly worn ARs, let alone a brand new rifle.

i have never heard of this, wich is due to the fact that ima new B, my 15-22 is really tight, and would really love to make the new one as tight. so where do i get these takedown pins and or wedges, i need to fix the front one too.

JP Rifles
DPMS Accurizing Wedge AR-15 - MidwayUSA

Don't do anything to the front pin. Either of these products will reduce the tolerance between the upper and lower at the rear takedown pin area, increasing overall tightness of the assembly.

thanx for all the info, prob try out both, not really sure how the jp one works though are they a reputable company?

The JP product is basically an adjustable diameter pin. I'm sure it will include instructions. Yes they are a reputable company.

I'd never seen this JP Tension Pin. Thanks Dragon88 I'm going to try one of these, because it looks interesting and I like the approach.

+1 to what arizona98tj said. I also have a 15OR with a bit much wobble for my picky taste, so I use the Accu Wedge. Works fine for me.

My 15OR is nice and tight, no looseness or wobble at all. Know someone who just got one and his has no looseness or wobble at all either.

Wonder if there was a change somewhere in manufacturing to tighten things up a little?

As far as using an accuwedge, can i just use some foam such as an earplug or will it get to hot and melt or come apart. what are the accuwedges made of?

Mine OR model, bought new in December, is as tight as it could be. Absolutely no looseness between the receiver halves. It was one of the things that so impressed me with the fit and finish. Practically flawless. Lower serial number SN 25XX so I guess it was new "old stock". I feel lucky to have drawn this example and it is scary accurate compared to a couple I have fired (other brands owned by friends).

The accuwedge is a kinda firmish hardish plastic rubberish thing, kinda like one of those pencil erasers but different. Its actually pretty soft, but a foam earplug is a little too soft though for prolonged use, you could stack up a couple of them and they will last for a while.

The accuwedge actually separates the upper from the lower by a bit. It acts like a wedge is suppose to do - it forces the upper and lower apart by the amount of the looseness. I'd go with the JP screw if the slight looseness really bothers you. The wobble can happen because there is a little excess space between the takedown pin and the hole it goes through when pushed in. This could be because of a slightly undersized takedown pin or the hole is slightly oversized. The accuwedge pushes up on the part the hole it at and forces the bottom of the hole up against the pin thus taking up the slack.

You can go to Lowes or Home Depot and get a flat nylon washer for about a buck fifty (cheaper than the accuwedge at midway and no shipping cost). Trim it up a little. It will do the same thing as the accuwedge (only it will be round ) I've seen people do this and it works, the only problem is you have to trim it exactly so it fits and applies pressure properly because the nylon does not compress like the material in the accuwedge does so you have to press down a little to get the takedown pin in. I don't like the washer method because if it gets loose it can find its way into the trigger group area.

Or....

Get some hobby/craft thin walled tubing at a local hobby/craft shop for about $.50 to $.75. The same inner diameter as the take down pin and the same outer diameter as the hole the pin slides through. Cut a piece with a pocket knife and use it as a spacer, insert it in the hole the pin slides through. It takes up the slack there. I did this on my Colt, worked great, cost me like $.30 or so back then.

Or....

Get a large pencil eraser, one of those red hard rubber ones, I think like $.99 or something. Trim it up with a pocket knife to make your own accuwedge.

Or....

Find yourself one of these (about $5.00 depending on where you get it surplus - up to about $30.00 new from someplaces - I think Granger has them - cheaper than the JP pin which is actually a different type of tension pin):


Ring handle positive locking pin

I've seen people do all sorts of things that worked. I used the spacer method on my colt, and later replaced it with one of those pins in the pic above.

WOW u are just loaded with useful info, i am going to try one of those ideas just not sure which one, being my serial number begins with 19 that means it is older? also do u think if i contact smith about this they would fix it, i bought the sw thinking it was superior fit and finish, but this looseness is annoying the **** out of me, and probably slightly affects accuracy. i was just so caught up in buying this that i didnt really do a thourough checking of stuff,by the way thank you for the help

The looseness doesn't really affect accuracy. I mean yes, its possible, but in reality, taking into account the shooter and the effects caused by the shooter, is the difference between approximately 1/16th of an inch at 100 yards with a little looseness and without really a concern? A weapon of this type - standard supplied parts and all - is still well within its specs of possible accuracy of 1 MOA. There is a lot that goes into it, but overall accuracy in relation to a little looseness is not a concern really.

So the looseness, if its not too great, is really more annoying than anything.

Where are you getting this figure of 1/16th of an inch?

Again, the lower receiver has ZERO effect on accuracy. The only time it could cause an issue is if the upper receiver is flopping around so wildly that the sights/scope/optic cannot be help steady. You would be hard-pressed to find an AR worn to this point. So just keep in mind that if you spend money on one of these devices you are "fixing" a problem that doesn't exist. But there's a lot of that going around in the AR market so do what makes you happy.

Were not talking about the lower receiver.

Mathmatically it works out to approximately 1/16th of an inch depression at 100 yards in line with the barrel centerline if the looseness remains when the weapon is fired, but the looseness does not remain when the weapon is fired. In reality it works out to nothing of concern. The Army looked at this issue more than several years ago on some versions of the weapon, turned out to be a non-issue. I was part of that testing.

It isn't lower receiver, its the upper separating from the lower slightly at the rear, moving up slightly at the rear (pivioting at the front take down pin) due to space between the rear takedown pin and the hole it travels through internally to hold the rear of the upper to the lower receiver. The part with the hole is part of the upper receiver. If that pin is slightly undersized, or the hole is slightly oversized, there is an amount of play - this is the looseness rattle. Thats what the accuwedge does, it forces the hole up against the pin thus eliminating the looseness.

Pull out the rear takedown pin on the M&P 15 5.56, open the weapon up, and you will see what i'm taking about towards the rear of the upper internally just under and at the end of the bolt carrier. Thats the hole the takedown pin goes through to hold the rear of the upper to the lower. Thats where the looseness originates in most of the weapons.

The looseness can also be at the front takedown pin as well but this is less common. Looseness can also be cause by the holes on the lower receiver on the outside that the pin travels through being slightly oversized, its the same effect as the internal hole on the upper being slightly oversized, or the pin being slightly undersized, the accuwedge still performs the same function in that case as well by applying upper pressure to the internal take down pin hole area thus forcing it up along with the pin so the pin meets the upper part of the external holes in the lower.

When the weapon fires, and there is some play in there because of the looseness, the upper is forced back and up on the front take down pin pivoting the upper rear down into position where the looseness is eliminated at that point at time of firing which is the reason why the effect of a little looseness is negated mostly as the upper sort of "self corrects" in that aspect by re-seating in a no-gap aspect for that instant thus eliminating any upward movement of the rear upper as the bullet leaves the barrel. If the weapon is zero'd with the looseness, it will fire the same each time in this respect so it will always remain zero'd for all practical purposes.

Of course this assumes the average very small looseness perceived by some. If there is a lot of slop there then there is a problem.

Its a non-issue really for accuracy, its more of a perception annoynance then anything.