Can't get the rear takedown pin to fit
 

I'm building a pistol that will eventually be an SBR once my Form 1 comes back. My lower came in yesterday and I finally got a chance to test fit the upper and lower.

So either my Noveske lower is out of spec or my VLTOR upper is out of spec. They're so tight that I can't fit the rear takedown pin in without a mallet.

The upper is tight but workable with my two Eagle Arms lowers, but fits perfectly on my friend's PSA lower.

My RRA upper fits fine on the Noveske Lower.

When I squeeze the VLTOR upper on the Noveske lower I can see the bottom of the inside of the upper's rear takedown pin hole sticking up into the lower's pin hole. It's like the log doesn't hang down far enough, or the hole on the lug is a couple thousandths off.

I emailed VLTOR and they gave me a RMA to send it back for them to check to see if it's in spec, but in a stroke of frustration last night I decided to just clearance the rear pin bit grinding a little bit of off the bottom (figuring I can get a new pin if I want for a couple dollars. Now I have an out of spec pin that makes the upper and lower fit together like a glove.

With that out of the way, I spent the rest of the evening installing the barrel and rail. Now that I've got the upper assembled, I'm re-thinking sending it back to VLTOR to get it checked out. My fear is that with the pin ground down and metal exposed, that I'm opening myself up to rust on that pin. I want to get my Form 1 sent off, so I don't really feel like sending the lower back to get checked out if I have a viable work-around.

My expectation is that neither the lower of the upper are "out of spec", but more along the lines of having opposing tolerances that stack to cause the problem. Would I be better off just sticking with a slightly modified rear takedown pin? Any suggestions on how to treat the exposed metal on that pin to keep it from rusting?

VLTOR MUR-1(a?) upper
Noveske N4 Gen II Lower
Noveske 8.2" 300BLK barrel
Daniel Defense Lite 7.0 Rail
AAC 51T Muzzle Brake (goes with my AAC 762-SDN-6 that's pending)
VLTOR BCM Gunfighter Charging Handle
PSA Pistol Buffer Tube
PSA LPK minus FCG (not installed)

No LPK installed, BCG, or buffer in place. I'm not going to install the LPK until after the lower gets engraved and it'll be next month before I can buy the BCG and SSA-E trigger. Shown with a mag full of 5.56 for context.

http://wct.vg/wt/guns/sbr/pistol_1.jpg

I would send it in. I know its hard to send in a brand new rifle. However, having it out of spec will always bug you. Might be different if you had bought a low budget rifle, but you didn't. Get it fixed, and in a couple months, it will be like it never happened.

farmer2

Filing the pin is certainly cheaper and an easier part to replace than the upper or lower receivers.

I would sent it to VLTOR to be looked at. I would also suggest getting the lower checked BEFORE sending off your ATF paperwork. I wouldn't want to drop a Form 1 on a buggered lower.

wct097
The best thing you could have done was shoot it!:upeyes: Did you even try? Both my DPMS and complete PSA carbine were very tight when I first got them -now after many rounds they are just like every other AR I've used take down pin goes in and out just fine!:supergrin:

Do you have another rifle you can try them on? All my VLTOR uppers have been tight but after you get the pin and out a few times they loosen up.

Try it on another lower that's seen some use.

When your putting that much time, money and effort into a AR you want EVERYTHING to be right. I'd send the upper back.

Personally I think the MUR is a waste of money, just go with a YHM stripped upper from Brownells.

Why is the Vltor MUR upper a waste of money?

I think I'm going to disassemble the upper and send it in when I ship the lower off to be engraved. I'm also going to go ahead and send in the Form 1 for the lower to get that in the works.

I spoke with a really nice lady named Robin at the NFA branch yesterday. I specifically asked her what would happen if I had a shipping issue and damaged or lost my lower while my Form 1 was processing. She told me that if I needed to change the serial number on the Form 1 prior to it being approved that I could just call and ask them to send it back to me for correction. When I send in the corrected form with the new serial number, it would go back in the box without me losing my place in line.

Its a answer to a non existing problem. Mil spec uppers are more than durable enough. On top of that the MUR does not work with many upper receiver vise blocks.

A rifle can never have enough durability. The vice block thing is no big deal IMO. I just used my upper receiver action bock and cut a piece of my derlin kitchen cutting board to support the flat top rail, and off into the bench vice. Works like a charm with absolutely no flexing. The best receiver vice block I have ever used on an upper.

The upper is disassembled now, ready to go back. For the money I'm spending, you're right, it's annoying.

FWIW, I'm not convinced the MUR is worth it or that it's solving any problems. I actually am annoyed with the fact that the "M" in MUR stands for "Modular" when it is absolutely not modular. I went with it for two reasons, neither of which have to do with function. First, I think it looks cool. Second, I figured that if I was building an expensive & time consuming SBR with "high end" parts that I might as well see what all the fuss is about. Everyone talks about "high end" or "top tier" guns and parts being where it's at. I figured I might as well see for myself.

Can't shoot it. Don't have the lower assembled since it's going out for engraving. Don't have the trigger anyway. Bought a LPK sans FCG since I'm going with the SSA-E trigger. Can't legally put it on any of my other lowers either.

Very tight would be nice. Impossible to get in by hand is what I'm dealing with. No breaking in there. Have to use a punch and hammer to force it in and out.

Update: VLTOR confirmed the upper is out of spec and is shipping me a new one today. Can't say enough about their responsiveness. They had me on the phone giving me a RMA within an hour of me sending them an email complaining of fit. Then today, they got the upper from me and called me back in under 3 hours from receipt to confirm it being out of spec and that they'll be shipping me a new one today.

Now... just have to wait for Ident to get my lower engraved and back to me so I can test fit the replacement.