AR-- Upper & Lower will not fit

[Bill2e]

Just working on putting together a stripped lower.

Everything went fine (not my first)

When I tried to attach to an upper I could not get it together. It seems the take down & pivot pin hole are not lining up.

I can not figure out what is out of alingemnt.

Any suggesstion on what to look for?

 

[tju1973]

Brands of each? I am not saying you got a cheapo brand, but I have seen uppers and lowers that were not mil spec and milled incorrectly-- thus they had alignment issues...

 

[Bill2e]

Rock River Arm Lower. Smtih & Wesson Upper

 

[sarduy]

make sure you have the hammer down.... it may be touching the bolt carrier.

remove the bolt and bolt carrier and try to attach the upper & lower...

 

[kwelz]

Also make sure the buffer tube is not screwed in to far.

 

[Bill2e]

tried both of the above suggestions. I am confused.

I can get ether the pivot or take down pin in, but not both.

I have tried in on multiple uppers. Every thing apears right, but it is obviously not.

 

[sarduy]

pics?

 

[sarduy]

the buffer may be too deep... pass the detent...

 

[Bill2e]

Sorry, not pics. I put it all away and will play with it another day. The safe is behind some stuff and a pain to get to.

THe pivot pin is difficult to get in, but once I did I could not get the take down pin in.

It seems to be out of alignment, as there is an ever so slight gap where the upper & lower meet.

I am confused I am sure I installed everything correct.

I have two lowers consecutive serial #'s, the first build was fine, this one is not.

I am hopping I missed something simple.

 

[sarduy]

try the upper into the other lower..

 

[Bill2e]

I did, I took a factory Smith that works fine apart and tried the smith upper on the new lower.

and it would not fit. Then tried a different lower still no good.

I may just have a lower out of spec.

I messed with buffer tube with not luck.

I gues I try some more another day.

Thanks for all the Ideas.

 

[W L Johnson]

This may be a dumb question, but is the lower for an AR-10?

Edit: on second thought, this would be too obvious.

 

[rogertc1]

A S&W 22LR upper will not fit on a real lower.

 

[taliv]

everybody makes mistakes every now and then.

grab a pair of calipers and measure the distances between the holes

 

[Bill2e]

OK, What should that distance be??

 

[taliv]

http://www.biggerhammer.net/ar15/cad/ar15_lowerblueprints_unknownorigin.pdf

 

[7.62 Nato]

If you have another assembled rifle just swap uppers. If both uppers fit , your new lower's out of spec., if they don't swap then it's the new upper.

 

[Kurt_D]

RRA is known for "tight" lowers. Supposedly they mill their lowers that way to prevent slop in the upper to lower fit. As far as I can see: 1) you're the victom of tolerance stacking between those two receivers or 2) you actually have a defective lower/upper, stuff happens.

I did, I took a factory Smith that works fine apart and tried the smith upper on the new lower.

and it would not fit. Then tried a different lower still no good.

I'm a little confused, you said you tried a working upper on that lower and it didn't fit. The you tried a different lower for the questionable upper and it also didn't work? OR did you mean you tried another upper on that lower it was also a no-go? The latter sounds like a bad lower.

 

[chaser_2332]

it's your rra lower i have a A4 NM and i ran into the same "problem" not a bad thing in a sence if you like tight guns. take the front part of both halfs and put pin in, then take a little grease and put on both sides of the upper that the pin goes through you should be able to take a rubber mallet and tap the 2 together and it will loosein up over time if not you may need a little file work on the upper not a big problem

 

[Bill2e]

^^^^^Ding we have a winner.

Thanks for all the advice.

A little grease & a rubber mallet and we are in business.

It is together now, but very tight.

 

[sarduy]

good to hear it works

 

[HOLY DIVER]

i wonder if one could polish the inside of the hole on the upper with a some compound and free things up a bit?

 

[7.62 Nato]

If the pin fits the hole you don't want to make it larger. If the fit is TOO tight you would carefully remove some material at any high spots.

 

[sprocket3]

I am having a similar problems with a RRA lower and a Les Baer Upper. My RRA fits fine on the lower but the Les Baer is very tight.