Upper is from radical firearms. Lower was purchased from 80-lower.com. Not sure if they manufacture lowers themselves or bought 3rd party.

Front pins go in fine, but the rear part of the upper will not go down all the way. I test fitted the upper to my friends lower and everything fit fine.

Could it be the coating in the upper?  I've read so many different solutions, just don't know where to start.

Here is the link to the photos. Thanks in advance for the help.

http://i64.tinypic.com/1jujrs.jpg

Link

That's pretty ugly...

Sorry hear the links.

http://i63.tinypic.com/1oks93.jpg
http://i63.tinypic.com/wclugk.jpg
http://i66.tinypic.com/33wla12.jpg
http://i65.tinypic.com/ndsbon.jpg

Is that all the farther the two will close together?

From pictures, and the fact the upper works fine on friends lower, looks like one or both of your rear takedown pin holes was drilled off center of spec; most likely the left side. This pic tells the story...
Attached File

See it now. Agreed...takedown pin hole looks out of location, as stated.

What jig and how did you drill?  Hand drill or drill press? Straight through both sides in one pass from one side or drilling twice; once from each side?

ETA: brain hiccup... Rear takedown is pre-drilled on 80% lowers... I'd contact 80-lower to discuss if it were mine.

One more thing... specs for lower dimension can be found in many internet sites. You can use to measure yours to see what is/isn't in spec. Here's one example:
Lower dimensions

Yep that's the farthest it will come together.

Looks like closing the upper into the lower is very tight per rub marks (red arrow). Doesnt look like enough to completely cause the alignment problem, but you could do some milling on the rear pocket and see. Some factory lowers completely mill the full pocket and remove the wall (see  |X| ) which eliminates the rubbing issue. Worth a shot if all dimensions check out.

Attached File

Here's a better picture if the rear hole. But this time I was able to get the upper in more, so the pin is able to go in, but will not come out the other end.

http://i68.tinypic.com/2n745dz.jpg

You tried your upper on the friends lower, but did you try fitting your friend's upper to your lower? If his upper doesnt fit with your lower, then you know for sure it's your lower's pocket dimensions and/or take down pin hole alignment.

You're very close on your last pic, but you probably had to push really hard to get the upper seated on the lower, correct?  If so, I'd look at the additional pocket milling as I described earlier on your lower as it's probably the front corners of the rear post rubbing against the pocket corners at the divider wall. I had a brand new upper/lower set from Anderson that was tight on the rear pocket too and wouldnt close without a little bit of work on the front corners of the pocket which fixed it. Technically, you "could" lightly file the front corners of the rear post to remove the rubbing, but I'm not a fan of that approach since you'd still have a lower that might not play nice with other uppers...more of which you'll surely add to your collection if you continue to hang around arfcom...

ETA: mystery dupe posting...

Yes, I did place my friends upper on my lower and ran into alignment issue. I will do some milling to the rear pocket and see what the put come is. Because I was able to get one side of the pin in, I was going to just sand down the coating of the rear pocket.

I'll post with an update.

Thanks for all the advise, much appreciated.

There are a few things that can keep the upper from closing all the way. One is the cut out for the back upper lug in the lower needing the corners squared up or the web removed. Another is a raised area on the bottom of the upper hitting the web in the lower. Some uppers are not completely flush across the bottom just in front of the rear lug there is a slightly raised area following the curved opening until it reached the width of the lug on each side.

Well, just finished milling the rear pocket. Did a test fit, and no luck. The amount of misalignment is still the same.

Is it time to file down?

Does the upper fold easily into the lower after the extra milling? Can you post a new picture showing the rear pocket now?  From your last pic (below) looks like the takedown pin is contacting the left side just a smidge high. Can you confirm if the rear lug is bottoming out in the rear pocket? If so, rear pocket depth may be slightly shallow.
Attached File

http://i66.tinypic.com/307utea.jpg

Here is a photo after milling. The upper definitely slides in a lot easier. I don't think it's bottoming out

Maybe I made a bad assumption, but have you completely removed the rear takedown pin then closed the upper onto the lower just using the front pin? This lets you look into both rear takedown pin holes to see how the alignment of the holes in the rear lug align with the holes on the sides of the lower. Shining a light through the three holes (side|lug|side) will give the clearest view of how everything lines up (or doesnt).

http://i64.tinypic.com/2ir53pd.jpg

Here is a pic of the holes lined up with the upper in and rear pin out of the lower.

Definitely not lining up

bad advice warning smack the rear pin in with a hammer and beat the s**t out of the rifle should pull the rig into "spec" with its self anyway even if its not with everything else

Haha. I may end up doing that if I can't figure out what else to do. I'm getting to that point.

Ummm, yeah, really bad advice...

Op... last picture is a little fuzzy and it'd help if hole was also lit from backside.

Regardless, does the misalignment of the rear lug with each side look the same? For example, does the lug hole look like its too far forward/ rearward and/or high/low when looking inward from both sides? Or does one side look correct and the other is off?

If both sides don't look off in the same direction(s), then the lower was drilled wrong at the factory resulting in the side holes being askew. Time to call seller and request a new one.

If they both misalign the same amount forward/rearward, then you again need to request a replacement because it was drilled wrong at factory and I wouldnt recomment wallowing out the side holes to force a fitment.

If the alignment looks correct forward/rearward on both sides, then its a high/low alignment issue. The gap between upper and lower in your picture indicates it's unlikely the lug hole is lower than sides. So, if lug hole is too high for both sides, mill the pocket slightly deeper so upper will close tighter and the lug hole will be lower and then align properly.
Attached File

If I am able fit the pin in one side of the hole, how can both sides be misaligned? The pin is just slightly hitting the left upper hole of the lower.

Another thing is that I retried fitting my friends upper onto my lower and it slipped right in. Both pins aligned with ease. My upper fits his lower, his upper fits my lower. So this just confuses me why I can get my upper to fit.

So... originally you said "Yes, I did place my friends upper on my lower and ran into alignment issue."  now you say his upper fits on your lower.

The only change that occurred between your two test fits of your friend's lower was the pocket milling on the sides, right?  

And you haven't milled (lowered) the bottom of the rear pocket, right?

And the pin is hitting the left side hole slightly high, right?

Seems to me that you have a) a lower with a shallow rear pocket, or b) an upper with a slightly long rear lug.

For problem "a" (most probable), mill the rear pocket deeper. To verify, measure the depth of the rear pocket on your friend's lower and compare. Use a precision micrometer (available at many places including Harbor Freight for about $10).

For problem "b" (less probable) compare the rear lug length against same on your friend's upper. If yours is longer, remove a thin layer from the bottom of the lug with a file or Dremel tool. With condition "b", your upper could still fit your friends lower if its rear pocket is deeper.

All the dimensions and specs for uppers and lowers are readily available online so everything you check with the micrometer should match.

On the question of side holes not aligning, if the drill bit used in the milling process isn't plumb or square with the lower blank, one or both holes can be located out of spec. It's rare, but can happen.

Lastly, inspect the edges of each hole the rear pin passes through for rough corner edges and smooth them out with a small jewelers file (also available at HF, HD, Lowes, Sears, etc)

So... originally you said "Yes, I did place my friends upper on my lower and ran into alignment issue." now you say his upper fits on your lower.

The only change that occurred between your two test fits of your friend's lower was the pocket milling on the sides, right?

And you haven't milled (lowered) the bottom of the rear pocket, right?

And the pin is hitting the left side hole slightly high, right?


When initially placing my friend's upper on my lower, prior to milling the rear pocket, it did not fit.  But, after milling the sides of the rear pocket, my friend's upper would fit.  When I milled the rear pocket, I used the 80% arms jig measurements, and it would not hit the bottom of the rear pocket.  Maybe have to go slightly pass the given measurements on the jig?

Yes, the pin is hitting the left side hole slightly high.

I'll do some measuring tonight with my friend's upper rear lug to see if that is shorter than my upper.

Ok so I measured the rear lug on the upper. Comparing to my friend's, mine is about .01 longer than his. It is hard to believe that this could be the culprit, but could it be?

I'll have access to a dremel later this.

It's possible the long lug is the last piece of the puzzle. Your last pics show it's very close and that .01 may be the trick. Tolerances on these parts can be pretty tight and even parts from same vendor don't always play nice with each other.

Hope it resolves the issue. Let us know the result.

http://i67.tinypic.com/bjbfpj.jpg
http://i65.tinypic.com/24eb3ft.jpg

Finally, got it to work. Shaved down the rear upper lug a bit. But, I had to slightly raise the upper for the rear pin to go in, then slide in the front pin. But I guess as long as everything went in fine and functions fine?

Thanks for all the advise!

Nice looking AR!  Glad it came together finally. With time and more open/close actions, it should loosen up a  little and be easier to close. Now take that beauty out and enjoy it!