Upper doesn't fit

[CBR1000rr]

I finally received my upper from Surplus Ammo today. It was a free upper that came with the purchase of a Black Hole Weaponry barrel. The specs looked good and the overall price was right so I bit. Unfortunately, the upper doesn't fit my RRA lower. The colors match and everything looks right but the flange for the rear take down pin doesn't have the right shape and causes it to get hung up on the lower receiver. It looks like it could easily be fixed with a little file work but before I go that far, I am wondering if it is something I should return? It took me nearly 4 weeks to get it and honestly I don't want to wait that long or longer to get it back.

Should I just take a file to it and make it work or return it? I don't plan on keeping it black so the loss of the the anodized coating doesn't bother me. What say you?

 

[Jtgarner]

Ask VitaminK I file everything

 

[printcraft]

Does it look like something that was missed during machining?

Is your lower correct?

 

[CBR1000rr]

I've always been more of a "I can make anything fit" kind of guy as well but this is my first build and thought I might want everything to fit on it's own.

 

[CBR1000rr]

Does it look like something that was missed during machining?

Is your lower correct?

The lower appears correct and it looks like the upper is as well so I dunno

I will get some pictures soon and post them up for your opinions.

 

[jwatkins383]

Upper

Free upper?! File? Hell with that use a dremel...HAHAHAHA... but seriously a file would be fine.

 

[03A3]

Can you use a caliper to get some measurements? That would give you something to work with.

 

[Colt556]

If it was really just a little out of spec I'd slowly file it so I got a nice snug fit. Work slowly because you can always take more off but you van never put it back on.

 

[Martin Draco]

You could sell it and get a different upper. If you send it back for an exchange, the one they send will have the same issue. Aero Precison uppers (Surplus Ammo uppers), are all like that. They fit some receivers and don't fit others due to the rear lug hitting the rear of the inside of the rounded milled out portion of the lower. I have a couple of them and they seem to fit well on my M&P lower, Palmetto State lowers, LMT lower, and one of my Spikes Tactical lowers (high shelf). They don't fit my RRA and my other Spikes lower (low shelf).

Recently I placed the upper on my Spikes lower after firing about 500 rounds through the lower and it now seems to fit. Perhaps you could force it a bit and "Break it in".

 

[03A3]

I voted "file".
Locate the offending area and work slow as you test fit.
It may not take much at all to get it fitted.

 

[IncendiaryGunner]

RRA lowers of kind of known for being "tight".

I would likely just fit it with a file... look on the bright side - if you do a good job, you won't have any gap.

 

[Miles42]

the right touch with a file could bring results you could not buy.

 

[solution_zero]

RRA makes their lowers tight. The fit between a RRA upper and lower has no play.
LAR tends to make theirs pretty tight fitting as well.

Filing it will remove the Hardcoat Anodizing, leaving bare 7075 aluminum. I'd sell it, and buy another upper. Fine fitting steel parts with a file or stone is one thing, aluminum is another. JMHO.

 

[KoopaKGB]

I vote another option on the poll as others have said. You could sell it and buy another one. This also might take more time then you'd like it to.

 

[Hookeye]

RRA makes their lowers tight. The fit between a RRA upper and lower has no play.
LAR tends to make theirs pretty tight fitting as well.

Filing it will remove the Hardcoat Anodizing, leaving bare 7075 aluminum. I'd sell it, and buy another upper. Fine fitting steel parts with a file or stone is one thing, aluminum is another. JMHO.

Not a wear area= NBD.

Could Cerakote if OCD.

 

[tradertator]

I don't even know if I would file it. Might lightly sand it just to remove the finish. I've had sever RRA uppers that were super tight at first when mating to the lower.

 

[jrainw]

RRA lowers are tight, I'd file the upper to fit.

 

[Mr Evilwrench]

Find specs. Get caliper. Take measurements. Fix the one that's wrong. Most likely, that will be the upper. Looks like the spec for the width in the front & rear of the lower is 0.500 +0.000/-0.004. Removing hard anodize from the sides of the lug on the upper is no thing; it just sits there. Might want to coat it with something, just watch the dimension.

 

[CBR1000rr]

Thank you for all of the input!

After investigating the issue longer than I probably should have, I ended up taking a piece of 1000 grit sand paper and an old dried up sponge (to give it a little backing but not to firm) to the rear lug. I took off enough to give the rear lug a slight curvature that matched the profile of the lower and got it to the point where it finally fit with a slight amount of force. The upper is still stripped and when mated to the lower, I am not able to pull them apart without the assistance of a wooden spoon. I'm sure all will be puppies and rainbows once I have the upper completed!

Again, thank you for the input. I wish I had an easier way to upload pictures but I just haven't taken the time to create a account to host the photos. I am beginning to think I need to get this done?

 

[tradertator]

Good to hear it. I actually love when an upper and lower mate that close. Can't stand it when there's wiggle in the action.