What would you do?
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Old 02-08-2012, 11:40 PM   #1
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Default What would you do?

I bought a brand new LMT CQB MRP 16" AR and right out the box it had a really sloppy fit between the upper and lower receiver. My bro in law got his a day after me and his has virtually no play.

After a couple e mails the senior R&D at LMT graciously said I can send it back and they will take care of it.

Here's my dilemma....... this rifle seems to be extremely accurate. Using basic Federal XM 193 ammo and if I am shooting carefully with the scope, I might get 3-4 shots all connected and 1 or 2 a little wider off the group.

Should I just get a JP AR tension pin or send it back and risk getting back a rifle that is not as accurate? For example if they change the upper and swap out the parts and some relationship between the barrel and receiver is different.

I prefer precision shooting when I go to the range so accuracy and consistency is important to me.

Thanks.

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Old 02-08-2012, 11:47 PM   #2
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A little play between uppers and lowers is not unusual and will not negatively impact accuracy. That said LMT's are not cheap. I just upgraded my bushmaster with the same LMT upper you've got so I know.

Personally, if it's grouping well with mill surp ammo I would not sent it back and risk an upper receiver swap. I've never needed
the accuwedge but I think I'd go that way first.

Tack

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Old 02-08-2012, 11:50 PM   #3
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I dont think that you will have anything to worry about if you send it back to be corrected, the slop in the receivers "can" also cause accuracy problems in itself, not always but it can.

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Old 02-08-2012, 11:52 PM   #4
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Movement b/w receivers won't cause any problems. If you're worried get some electrical tape. Avoid the acu wedge, they fall apart and can be an issue.

How big is the gap? Penny? Dime? Piece of paper?

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Old 02-09-2012, 05:37 AM   #5
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Quote:
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How big is the gap?
It is significant, to my way of thinking mj. I would say just a hair under a 1/16" from one way all the way to the other side. I can make the gun "clack" by holding the buttstock secure and moving the upper side to side.

I know AR's are typically loose and some say they shoot looser. I dunno, maybe I expect too much from a $1700 battle rifle.

This whole accuracy thing I see as sort of a bone of contention..... with some people saying a loose fit between receivers will NOT affect accuracy at all, and others who say it will. I understand that both sights are on the upper receiver and you are sighting across the same platform.HOWEVER....... what if the play was a 1/4" between receivers? It would be barely shootable. It would "bend" in the middle and sighting would be horrible.

So how much is truly acceptable? What is the clearance specification or within normal limits? The more I think about it the more the JP Enterprises Tension Pin seems like a good fix. I don't mind needing an extra tool. If I ever found myself in a SHTF scenario, I could always go back to the slop so as to have a quick tool free takedown if needed.

BTW, I bought two accurizing wedges a while ago hoping they would take out the slop, but they will not fit. I have a high shelf lower and these are designed for low shelf models.
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Old 02-09-2012, 06:00 AM   #6
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It's obvious that this bothers you. I'd recommend sending it back. If I spend 1700 or 700, and want happy, Id give the manufacturer a chance to make good.

In my personal opinion, its a judgement call. How much play is too much? Dunno, how about posting a vid? We might be able to give you a better recommendation.

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Old 02-09-2012, 12:21 PM   #7
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How about sending it back and emphasizing that you'd like them to work with the existing upper, since you seem to be happy with it?

I would think they would prefer to swap out lowers than uppers, anyway, if they can achieve a tighter fit by doing so.

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Old 02-09-2012, 04:16 PM   #8
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Quote:
Originally Posted by Fumbles View Post
It is significant, to my way of thinking mj. I would say just a hair under a 1/16" from one way all the way to the other side. I can make the gun "clack" by holding the buttstock secure and moving the upper side to side.

I know AR's are typically loose and some say they shoot looser. I dunno, maybe I expect too much from a $1700 battle rifle.

This whole accuracy thing I see as sort of a bone of contention..... with some people saying a loose fit between receivers will NOT affect accuracy at all, and others who say it will. I understand that both sights are on the upper receiver and you are sighting across the same platform.HOWEVER....... what if the play was a 1/4" between receivers? It would be barely shootable. It would "bend" in the middle and sighting would be horrible.

So how much is truly acceptable? What is the clearance specification or within normal limits? The more I think about it the more the JP Enterprises Tension Pin seems like a good fix. I don't mind needing an extra tool. If I ever found myself in a SHTF scenario, I could always go back to the slop so as to have a quick tool free takedown if needed.

BTW, I bought two accurizing wedges a while ago hoping they would take out the slop, but they will not fit. I have a high shelf lower and these are designed for low shelf models.
It obviously isn't effecting accuracy from what you've shared. You'll find certain manufacturers that make claims about fit and finish and even consumers that talk about the fit and finish of their ARs. I find it is usually smoke and mirrors to pull attention away from the things that actually matter.

In the end if it lowers your confidence it's a problem.

Just remember to tight can be an actual problem.
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Old 02-09-2012, 04:51 PM   #9
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I have one that matches my upper to my lower perfect in the lines , My other other not so much .its off a bit which really doesnt bother me, but its a little looser , I dont notice any more accuracy out of it than the other but if I had spent $1700 and wasnt happy with the movement I would send it back and see if they can find a better fitting lower since your happy with the way the upper shoots . Im sure they would rather go that route to make you happy rather than replace a upper that your already happy with .
Just my .02 cents and how I would approach it

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Old 02-10-2012, 07:57 AM   #10
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I wrote a big 'ol long reply, went to do some stuff, came back and went to preview it and the timeout made me lose the post. Now I am a little burned out from a long day to do it all over again.

Thanks for all the replies. I really appreciate it. I am going to chew on it but I am sensing it might be best to leave well alone. I think I am going to try using shimstock. If I do I want to do a with and without accuracy comparison.

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