Ar lower and upper fit

[Vamptepes]

I am putting together my first AR. I have a AR57 brand lower and a Alexandria Arms stripped upper. Just installed my stock kit so was trying fitment of the upper and lower. It won't go together. I tried my del-ton upper that's done and it's the same thing.

Installing upper by using front pin first then seating it the rest of the way. There is maybe 1/8inch gap or less. Rear takedown pin just won't go through. Tried smacking it with my hand and nothing. Also tried moving the parts in and out to see if i could see some wear on the new finish to figure out where it is catching at. So far i cannot find it. Not sure if it's the lug or the back side of the upper.

Any ideas? Find the problem and file it down??

 

[Sainte]

Before you do anything, PICTURES!

measure twice, cut once.

also look too see if there is a tension screw under where the pistol grip goes. Some companies put a small flat head or Allen set screw in here which will protrude thru to the inside of the lower receiver and contact the bottom of the rear take down pin frame of the upper to remove any slop when the two are mated and pinned.

inside view:

http://www.recoilweb.com/wp-content/uploads/2012/05/rainier-arms-lower-tension-screw.jpg

bottom view:

http://www.tacticalinc.com/images/productextras/smarf1-8-500.jpg

 

[Vamptepes]

Let me know if you need other pictures. Also there is no tensioner screw. It seems to be hanging up on the back side but can't really get a picture of it. Weird angle and bad lighting makes shadows and a terrible pic.

 

[Tydeeh22]

Look at where youre getting friction at the end of the upper and the threading of the lower for the buffer tube. Looks like a mill job went awry.

 

[jd4320t]

My 9mm Aero Precision upper was the same way. I removed material until it fit.

 

[Vamptepes]

I guess im just nervous. I have a dremel but dont want to use it. I have some machinist files. I imagine that would work. I just domt want to mess anything up. I've had nothing but problems with this build. The first was my trigger was junk and had to wait on a replacement and my parts keep getting lost by ups.

 

[jd4320t]

Definitely don't need a dremel. Sandpaper or some easy filing will get it done. Just do a little at a time.

 

[Vamptepes]

Ok. I was looking at it thinking it was the lug but I dont believe it is. It is rubbing the back pretty good. So I assume I should be taking the excess metal off the lower. Doesnt look like it should be much to get it to fit. Just need to remember to do it evenly lol. God it's frustrsting though

 

[jd4320t]

oh dang..I figured it was the lug

 

[Vamptepes]

Yea I can tell its rubbing on the back so I guess i'll remove some metal there. Check again etc. im not gonna worry about it to much about it since that gun is going to stay together and im not swapping things out on it.

 

[hrearden]

Go a little at a time and keep that fit tight.

 

[Vamptepes]

I still haven't messed with it yet but i did place the upper on the lower without attaching pins. If you do that both holes on the upper are slightly off. So i figure i can just go ahead and attach the front pin again and file it down for a custom fit. I am going to shave the sides and the back of the lug a bit first since i've noticed quite a lot of rubbing on the finish in those place. But i may just need to file down the inside of the back of the lower a slight bit not much. I'm gonna guess it's not going to mess anything up. I rather take a bit of the lower then the upper. Don't know what all kind of stress the upper takes and don't wanna risk weakening it or something.

 

[NinnJinn]

Take it with a grain of salt ok? I'm on my first AR build as well. But in the pic you posted, I noticed your safety is on... Doesn't the hammer have to be cocked before the safety will engage? would that have anything to do with it not fitting properly?

 

[Vamptepes]

Yes hammer has to be cocked for the safety to engage. And no it shouldn't effect anything. I've taken my other gun apart either way with no problems. I think before i do anything i will take my other gun and get my calipers out and measure the lugs on both and the spacing on the lower.

EDIT: I found to things wrong. The back part of where the lug would go in the lower is out of spec slighlty. I'll fix that by shaving the lug a bit. And then the lower where the buffer tube goes in protrudes to much. I removed my stock kit so i can see inside to get a better idea where it was rubbing. You can tell it's catching mainly on the back. I'll be filing that all down first then test fit and go from there. I rather shave the lower rather then the upper even though many people say modify the cheaper part first. I rather deal with the problem itself. Plus if i did want to swap my uppers around i don't want to have to modify another just to go to that lower. All this should be done hopefully by Wednesday when i have more time. I'm glad i bought a set of calipers for reloading they come in handy a few times for other things.

 

[rvb]

personally, I would find out which part is the problem part (using other known-good upper/lower receivers) and get the manufacturer to make it right. Who knows what else is messed up. If it's the lower, for instance, and they lost their index point mid milling, who knows if the trigger group pins, mag release, etc are right. These aren't oversized fitting-required gunsmith parts, you shouldn't have to touch them with a file.

my 2c.

-rvb

 

[rvb]

Just went back and read through the thread and noticed the following comments you made....

I tried my del-ton upper that's done and it's the same thing.

ok, so you know it's the lower.

I've had nothing but problems with this build. The first was my trigger was junk and had to wait on a replacement and my parts keep getting lost by ups.

please read my comment above again... who knows if it really was your trigger group that was bad, or if this lower is just trash. Get a new lower before you start filing.

Who knows what else is messed up. If it's the lower, for instance, and they lost their index point mid milling, who knows if the trigger group pins, mag release, etc are right.
-rvb

-rvb

 

[Vamptepes]

It was the trigger group i've got a replacement installed. The guys at profire have been helping me out through all the headache and we've tried numerous things when it came to that. I've taken tons of measurements and everything is g2g in other spots. I'm not going to bother dealing with another manufacturer they give me headaches. Plus i was going to mill my own lower anyways so it's not a big deal to shave a small bit off. If it was something larger (way off) i would def be calling them but seeing as how it's a tiny fraction off i'll give them the benefit of the doubt. Honestly it may just be the thick anodizing on both parts and may just need knocked down. I know the upper is super gritty and almost chalky feeling.

I appreciate your input don't think i'm blowing you off but i do believe it to be minuscule milling mistake. Especially since it is a lower serial number lower for that company and they specialize mainly in uppers.

 

[Sainte]

get the lower replaced by the mfg! the second you start filing on it, you are stuck with it. I have seen this in DPMS once or twice, Olympic a few times as well. I'm sure all mfg have their "oops" moments tho.

bottom line, don't mess with it unless you really can afford to throw the money and time away. I'd also have the company refund your money for the new lower parts.

 

[silentvoice71]

Either mill your own or get a good well known lower... Some of these pop up companies are good and some are bad....very bad. I mill my own so i am at fault if i screw up

 

[jhparsons78]

I had the same issue. Just take a Phillips screwdriver and gently line the holes up. They are made to have a tight fit. Then keep working the pins in and out until they loosen up.