So I just got my upper in the mail last night. Very excited.
I go to put it on Rock River Lower, and it would not go on. The pivot pin goes in nice and smooth, but when I bring the two halves together, it will not join. I did try and force it, but I couldn’t get the take down pin all the way through, then it was a beast getting them apart again. The part on the upper that has the holes for the take down pin hits the lower (hope that makes sense) and does got go in nice and smooth like it should. I pulled out the BCG and the buffer just in case that was the hang up, and it still won’t go…
Sooooo, I figure it’s just the lower. I try it on my Larue lower (no-go) and a Magpul (:D) lower and still no go. I’ll try it on a couple more lowers for the hell of it, but this just ain’t right.
I know this company will take care of it. But my question is this: when they test fire a weapon at the factory, do they even mate it to a lower? I don’t see how. I’m sure they would have picked up this discrepancy if they did, or if I bought a complete rifle from them…
I have an upper right now that appears to work on every lower I have tried it on, except the one I want it to go on (it’s an SBR upper), and the original upper that goes on that lower won’t fit on anything else. It’s a factory Colt 6933, and while I have no intentions of changing the gun in the long term it was a bit aggrevating to not be able to mount up my new upper. Sometimes it’s just a matter of tolerance stacking. And there’s no guarantee even if you buy a complete rifle that the parts will work with other parts. Sometimes it’s just a bad luck of the draw. But if you bought the upper from a reliable vendor or maker you’ll obviously be fine, and your situation is just one more reason to buy from known entities with reputations for good service as well as good products.
I called them. They said that it’s built that way on purpose and it would get better with time. He said if I didn’t like it, then they’d be happy to loosen it up or whatever they do. It’s a VLTOR MUR upper receiver, and he said they’re just made that way with the extra paint and anodizing.
I’ll try and get it on the lower again I guess and go from there. Just have to bring a hammer and punch to take it apart at the range. Hopefully it’ll loosen up.
I have 4 Vltor uppers, they are picky. 1 gen MUR will only fit with a certain gen POF, and another took out some material in the lower fitting it.
Also, the only time I have ever had to heat an upper (really hot, in oven + frozen barrel) to fit a barrel was in a VIS.
I have taken a break from them between the fitment, and the new gen forged uppers having rough finishes and some with gouges under the anodizing, although i have not gotten a newest gen with the angled deflector.
It won’t go on the lower I want it to. I have limited options here though as it’s an SBR configured upper and I can’t legally even try it on non-SBR lowers. I have one other 6933 to try it on, and a 9mm SBR that I’ll try it on as well to be sure.
I tried putting one other non-SBR upper on my troublesome 6933 lower and it had fit issues as well so I’m not entirely sure if it’s the MUR or not yet. Kind of annoyed right now at having to dick around with it instead of just dropping it on.
I can’t get the pivot pin in at all. Whether I start with it “open”, closed, takedown pin in first, nothing. The pivot pin just won’t go in.
I haven’t had the pivot pin problem on the 5 or so lowers I own. But when I went to the dealer I picked it up at (to get the shipping box in case I return), we were talking about it and he wanted to try it on a RRA lower he had. The pivot pin was WAY tight, and we couldn’t get it to fit in the rear.
SO, do I return and have them make it so it’ll fit a bit better, or do I just force it on the lower and hope it loosens up some? I think I’ll force it and shoot it first.
I think you will find that all of the VIS and MUR are built to be tight. Tap the pin in the rest of the way, and it will flush up. You will probably have to tap the pin back out with something as well. As you shoot it, it will loosen up.
Think back to when you were in the military. Some of the weapons off the rack were loose, and some were so tight you needed to use an object to push or tap the pins out.
Tolerance stacking with RRA components like the OP’s lower is a norm, not an exception, and should be expected. Despite marketing to the contrary, their typically tight fits and “better than spec tolerances” aren’t usually a good thing.
There is certainly a difference between tight and not-fitting. The OP has commented that his take down pin presses part way in, which is how mine are, they are tight, and need to be tapped in the rest of the way.
Rob says his won’t go in at all, which is a different issue.
The problem when dealing with internet “issues” is that you don’t know what you are really dealing with. A guy who is used to push pins slopping in and out is going to be very unhappy with a MUR or VIS. A guy who is used to hard pressure when pressing pins in or out probably won’t be all that excited or upset. I don’t say this referring to the OP, I mean it as a general comment when talking about online issues. All to often it becomes a matter of a faulty trigger actuating nut.
Well, gentlemen not to jump on the bandwagon but I have a new gen. MUR that is also extremely tight fitting, as in tapping pins in and out of not only receivers but also my upper rec. block for installing barrels. I know of many people who like super tight tolerances between their upper & lowers. I personally like a little slop!
