URX Rail on 9" Upper Misaligned?

[Meridian]

I just received my new 9" AAC 300BLK Upper. When I pulled it out of the box I gave it a once-over to check for defects, etc.. I noticed the URX3 rail is canted down slightly and to the left relative to the upper receiver (see pics).





You can see the misalignment when looking down the top rails from the rear. Is this normal for the 8" URX3?

I also noticed I have "the gap" between the rail and the upper receiver.


Normally I wouldn't pay much attention to it since it's cosmetic. However, in my case it throws off the spacing between the recoil grooves by ~1mm between the rail adapter & the upper receiver.


Are all of these alignment issues normal, or did I just get one that was made at 4pm on a Friday before a holiday weekend?

[300Blk]

The KAC URX is not a continuous rail system with the upper. You can't mount accessories that span the two rails. It is not a monolithic-style upper. The gap is normal - you install it by screwing it on as tight as it can go, and then backing off until the rails are aligned.

It should be aligned in rotation though, but I can't tell from the photos if it is or is not. A top photo without a ruler blocking the view would be best. But if it looks rotated to your eye, then you can ask for an RMA.

[haw1144]

My 9" was off when I first took it to the range... it didnt even touch paper at 50y...had to crank windage all the way to the left.

I did the ghetto test by just flipping up the irons and setting the rifle upsidedown... only 1 ear on the front sight was touching and the other was off. Figured it was canted.

Sent it back to AAC and it took maybe a week or two... and got it back. Pretty simple/easy process... great CS. Tried it out at the range again. It still required some windage adjustment to the left, but not as bad as before. I just left it as is... shoots fine otherwise once zero'd in.

[Meridian]

The KAC URX is not a continuous rail system with the upper. You can't mount accessories that span the two rails. It is not a monolithic-style upper. The gap is normal - you install it by screwing it on as tight as it can go, and then backing off until the rails are aligned.

Okay, good to know about the continuous/monolithic vs. spanned rails.

It should be aligned in rotation though, but I can't tell from the photos if it is or is not. A top photo without a ruler blocking the view would be best. But if it looks rotated to your eye, then you can ask for an RMA.

The URX top rail appears to be aligned with the upper receiver rail where they meet. However, when looking down both rails from the rear of the upper, the URX rail drops off ~1/32" over the 8" length as it goes toward the muzzle. Here's another pic (camera's not the best).



The yaw to the left is noticeable when you hold a straight edge against the right side of the rails. You can easily see the drop with a naked eye, but the yaw to the left isn't as clear without the straight edge as a reference. The URX doesn't appear to be rotated relative to the upper receiver. However, it does give the impression that it may be either slightly twisted down/left itself or that the rail is not entirely square to the face against the receiver.

Again, all of this may just be normal for free floating tubes on a 9" barrel. I just want to know if it's me being picky or if something wasn't quite right.

[300Blk]

As for if you are being too picky, I don't think so. You can expect that those two surfaces should point in the same direction. I would ask for an RMA and state that the top of the KAC handguard not being square to the rifle upper. It probably needs the handguard replaced. BTW, no rush. If you want to enjoy your rifle for a while, you can do this at any time and deal with it off-season.

[Meridian]

BTW, no rush. If you want to enjoy your rifle for a while, you can do this at any time and deal with it off-season.

Also good to know. I was thinking at the very least I should run some rounds through it just to make sure there wasn't anything else that might merit attention.

[dustyroads]

I had a similar issue with my 16 incher i posted about in AR15 board. Shot them an email and within about week i was given an RMA, sent it in, it was fixed and sent back. They replaced the rail for me and test fired it. I'm happy with the fit and finish and Brent was helpful.

[tater_ga]

Thanks Dusty.

Send me an email and I'll get you an RMA sent out. We don't really police the forums. So, please let us know when you have an issue so we can get you taken care of.

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