View Full Version : NSR 13.5 rail and BCM 16" upper. Something is crooked.
Today I assembled my new 16" LW BCM upper with a NSR 13.5 rail. Something is off center.
I can't tell if it's the rail or the barrel. When I look at it from the end, and from the top or bottom, it is definitely closer to the left side of the rail by several millimeters. It's enough that I noticed it almost immediately after finishing the build.
I am leaning toward the rail being the culprit, because when looking down the barrel from the rear of the upper, I can't see any sort of bias to the left at all. It appears perfectly straight. I did notice, however that the barrel was VERY hard to remove, much more so than previous uppers.
Two questions:
-How can I narrow the problem down to the barrel/receiver or the rail?
-Is this something that can be caused by improper torque on the barrel nut?
What torque spec did you use? What upper are you using? Does it have the index pin?
I would possibly remove the rail, slide it back into place and then use an optic mount like a TA-51 and clamp it to the upper and rail while you tighten the screws. down.
Today I assembled my new 16" LW BCM upper with a NSR 13.5 rail. Something is off center.
I can't tell if it's the rail or the barrel. When I look at it from the end, and from the top or bottom, it is definitely closer to the left side of the rail by several millimeters. It's enough that I noticed it almost immediately after finishing the build.
I am leaning toward the rail being the culprit, because when looking down the barrel from the rear of the upper, I can't see any sort of bias to the left at all. It appears perfectly straight. I did notice, however that the barrel was VERY hard to remove, much more so than previous uppers.
Two questions:
-How can I narrow the problem down to the barrel/receiver or the rail?
-Is this something that can be caused by improper torque on the barrel nut?
What torque spec did you use? What upper are you using? Does it have the index pin?
I would possibly remove the rail, slide it back into place and then use an optic mount like a TA-51 and clamp it to the upper and rail while you tighten the screws. down.
Sorry I should have specified that the rail is "clocked" perfectly to the upper, but the end of the barrel is horizontally biased towards the left side of the rail.
I used the proper torque as indicated in the rail installation instructions. 40ft-lbs three times followed by final torque of a max of 80 ft-lbs. There is an index pin, but it doesn't specify how it is used. I am using a standard bcm upper receiver.
Cincinnatus
08-17-13, 09:25
Could you post some pics?
Failure2Stop
08-17-13, 09:53
I wrote about this a while ago.
Basically, the culprit is most likely your barrel extension or upper receiver.
The dimensions of those areas are not required by spec to be at the level of straightness that you need to ensure that your barrel will be perfectly centered inside a floating tube.
Still, it is not a functional issue, and if you can't get over it you can fix it with some work.
Typos brought to you via Tapatalk and autocorrect.
I wrote about this a while ago.
Basically, the culprit is most likely your barrel extension or upper receiver.
The dimensions of those areas are not required by spec to be at the level of straightness that you need to ensure that your barrel will be perfectly centered inside a floating tube.
Still, it is not a functional issue, and if you can't get over it you can fix it with some work.
Typos brought to you via Tapatalk and autocorrect.
Is this where those receiver truing tools come in?
Check to see if your gas block is touching the inside of the rail, or any rail additions you may have added.
I had a similar issue and found the gas block up against a mounted rail backing piece.
I too couldn't tell if my BCM 14.5" middy had a crooked barrel, barrel nut or if the 12" C4 rails were just misaligned.
I solved it by buying a VTAC ALPHA 13" rail, and installing that...it was worse than the C4s.
I just returned it to BCM, so hopefully it'll get fixed. With a pinned muzzle device, it's important to me that whatever future rails I put on it (that work with a standard barrel nut) align well.
--
If it's the UPPER, it would seem the barrel is also crooked right, or is it generally just the barrel nut?
(My post was deleted on TOS for fear of upsetting a sponsor...even though I prefaced it by saying I wouldn't name the manufacturer.)
eljimbo142
08-19-13, 21:03
There is an index pin, but it doesn't specify how it is used. I am using a standard bcm upper receiver.[/QUOTE]
the index pin is used with the VLTOR/Noveske upper
I had an NSR on my last Colt and didn't use the pin--would have required drilling a hold in the upper. I never had a problem.
I wrote about this a while ago.
Basically, the culprit is most likely your barrel extension or upper receiver.
The dimensions of those areas are not required by spec to be at the level of straightness that you need to ensure that your barrel will be perfectly centered inside a floating tube.
Still, it is not a functional issue, and if you can't get over it you can fix it with some work.
Typos brought to you via Tapatalk and autocorrect.
Is this where those receiver truing tools come in?
That's what I was thinking.
This issue has been reported twice this week with new builds.
Has BCM been replacing the barrels in question, or are they saying "If the gun works, we're not replacing anything."?
We'll see. Mine arrived there yesterday--waiting for a response/call or it to get shipped back. ::fingers crossed it gets fixed, not just realigned/shimmed::
We'll see. Mine arrived there yesterday--waiting for a response/call or it to get shipped back. ::fingers crossed it gets fixed, not just realigned/shimmed::
How much was yours off by?
The 12" C4 rails were probably just 3/16"...maybe even 1/4" closer to the barrel on the left and 1/4" further on the other side--it was definitely visible, but when I held it in place and tightened it down, I could get it to where it was barely visibly noticeable--sticking my two forefingers, one would go in a bit, the other wouldn't (so it was still off).
I have a feeling it might shoot itself out of alignment unless I used red loctite and/or a shim.
NOTE: The VTAC ALPHA 13"s were off even more...I wish I'd measured, but I'd say there was 33-40% more space between the barrel and the rail on one side.
I actually plan on running the VTAC until Fortis or someone comes out with a lightweight keymod that uses a standard barrel nut. I've now heard of 3 people with the same issue. Hopefully we'll all get it "straightened" out.
Failure2Stop
08-20-13, 16:48
Is this where those receiver truing tools come in?
Sometimes.
I'm not being intentionally cryptic, it's just that it can be in a few different places, or with a tolerance stack that isn't visible until 10" from the barrel nut.
If it's the threads, there isn't really anything you can do.
If it's between the barrel extension and the face of the receiver, they can be "flattened"; the extent of which work can be anything between simple and soul-crushing.
The big thing to remember is that the TDP doesn't control these dimensions as tightly as needed to have precise alignment of free-floated tubes and barrels; so you can have quality components all around and still have a "misaligned" barrel and tube. Frustrating, I know, but one of the results of advancing a design that was not specifically spec'd for that setup.
This is another guy, from TOS, who just put a Troy ALPHA on his BCM blem upper...my VTAC ALPHA was off exactly like this:
http://i803.photobucket.com/albums/yy318/talknguns/20130820_142057_zps93ceec5d.jpg
The problem there is mounting BUIS on the rig. You may or may not be able to adjust windage enough to even get it on paper. I had the same issue with a TRX Extreme on an unnamed upper. I was able to true that setup through judicious sanding of the interface and bridging the upper & forend top rail while torquing everything down.
And yes it was a pain in the ass. :(
Yeah, for a $1200 new (non-blem) complete upper group, I shouldn't have to do all that (in my opinion--we'll see).
My hope is that they just replace it with a new one that is dead-center aligned.
My 4 year old BCM upper had the exact same problem. Regardless of the rail system/barrel nut, it was misaligned. It also had other issues, so I replaced the upper receiver, which took care of it.
When I originally purchased it from BCM, it also had a slightly canted FSB (to the left, when looking down the rifle while firing).
So is this a quality control issue? Or something to be concerned about for future buyers?
I've only read of a few so far...
But if I hadn't switched to the 13" VTAC rails, I don't know if I would have cared/noticed...the 12" C4s weren't off by much (I think they can be canted a bit during install and look more aligned).
I defintely think it's something people should check (though I don't know how many people are going to try out a 2nd FF handguard). I knew I was going with a tube handguard, but they didnt offer it in LW and BHF, so I got the C4 to try out (and they are super well done and insanely lightweight).
I spoke to a gentleman from BCM today. I told him the details about the problem, and said that I would try sighting it in and seeing if I had any issues.
http://i51.photobucket.com/albums/f392/BiteyMcClaws/7f9c0afe-5887-4fca-8aed-15f8b8b7ea8e_zpsf7c2de3c.jpg~original (http://s51.photobucket.com/user/BiteyMcClaws/media/7f9c0afe-5887-4fca-8aed-15f8b8b7ea8e_zpsf7c2de3c.jpg.html)
Ned Christiansen
08-21-13, 17:07
The barrel extension flange surfaces, front and back, are out of parallel. A little bit here translates into a lot at 13.5". My guess..... seen it, in the extreme. Most people/manufacturers would not think to check for this
It probably will sight in with lots of extra windage.
I'm worried about mine because I tend to only lose 2MOA vertical when I switch the TR24G between my two old uppers...I sold one to get this, so I'd hate to have to crank the windage 30 clicks one way and back switching uppers.
Did they offer to replace or repair it, or just suggest you shoot it?
The barrel extension flange surfaces, front and back, are out of parallel. A little bit here translates into a lot at 13.5". My guess..... seen it, in the extreme. Most people/manufacturers would not think to check for this
Is there a way I can verify this with calipers or some other method?
Djstorm100
08-22-13, 09:00
Is there a way I can verify this with calipers or some other method?
Could use a square or a machinest square/ruler
Tooth & Nail
08-26-13, 18:23
1911-A1: Any update on the sight in and what, if anything BCM offered to do to rectify the situation?
evi1joe: Any feedback from BCM on your return?
I'm quite interested because I have a new BCM BFH 16" Mid Length LW upper that I'm planning to install either a NSR, or one of the new BCM Handguards (when released) on. The FSB has to be shaved to do this and I'd be pretty disappointed if the end result isn't a centered barrel. Thanks.
It will arrive Wednesday--I'll post back then after I take off the C4 and put on a VTAC...the extra inch and the circle-tube shows any misalignment more. Fingers crossed.
When I asked them if they could tell me what they did to it, I got what seems like a generic reply:
"We inspected, repaired, replaced parts as necessary, & test fired, you are good to go. Enjoy!"
Here's hoping I am GTG.
Tooth & Nail
08-26-13, 18:35
evi1joe: Thanks very much for the update. I really hope it's squared away when you receive it. Looking forward to hearing how it works out and your thoughts on what they might have done.
Djstorm100
08-26-13, 21:05
I subscribed because I was curious in hoping that they would find the true cause of this..fail lol. Glad you got it worked out though.
I have installed several NSR rails. I have found a few of them to be crooked. Troy Alphas and NSRs are extrusions and this is common in those types of products. A machinist for a very well known company that many people on this board buy from, showed me how to look for crooked extrusions...
This thread is very much making me reconsider the sum total of my in progress 6.8 build. I've yet to purchase the barrel and forend. I was down to an NSR (preferred) or Troy Alpha with integral front BUIS.
The parts bin currently has a Vltor VST-1P sight tower/gas block I picked up on sale. I think whatever forend I choose will be notched to utilize this piece. Off center sights trigger my OCD, badly. :(
Jerseymike
08-27-13, 06:38
I'd say it'll definitely present a problem when and if you mount irons. You'll more than likely run out of room on the windage knob.
TacticalTyler
08-27-13, 08:55
My 4 year old BCM upper had the exact same problem. Regardless of the rail system/barrel nut, it was misaligned. It also had other issues, so I replaced the upper receiver, which took care of it.
When I originally purchased it from BCM, it also had a slightly canted FSB (to the left, when looking down the rifle while firing).
My 14.5 upper was the same way. Canted fsb. The rifle ran great an held zero with lots of Windage adjustment.
Just wasnt expecting to look like that coming from bcm.
I understand a cheap wasr-10 ak to have canted sights on it. Not a quality bcm upper ? Gun still ran great, just little annoying tid bit I guess.
It probably will sight in with lots of extra windage.
I'm worried about mine because I tend to only lose 2MOA vertical when I switch the TR24G between my two old uppers...I sold one to get this, so I'd hate to have to crank the windage 30 clicks one way and back switching uppers.
Did they offer to replace or repair it, or just suggest you shoot it?
Wait, hold on. Why would rail barrel alignment matter with an optic, unless your mounting it so far forward it's on the rail instead of the upper? I would think you would run out of eye relief before then.
glocktogo:
I've had two NSRs, a Troy extreme and Alpha--all were GTG. There's like a .02% chance you'll have any problems.
foxtrot:
IF the barrel/upper is crooked, then moving my acog or T1 from a straight upper to a crooked upper/barrel would mean my optics would be off...I mean, I don't move the T1, but I remove it and use the acog on that upper some and it's just off a tad with the two current uppers/ARs, BUT I only have to adjust elevation 8 clicks and I'm back on (so far!).
If my new upper comes back still out of whack, and I kept it, I bet I'd have to do a lot more windage adjustment than I'd like.
glocktogo:
I've had two NSRs, a Troy extreme and Alpha--all were GTG. There's like a .02% chance you'll have any problems.
foxtrot:
IF the barrel/upper is crooked, then moving my acog or T1 from a straight upper to a crooked upper/barrel would mean my optics would be off...I mean, I don't move the T1, but I remove it and use the acog on that upper some and it's just off a tad with the two current uppers/ARs, BUT I only have to adjust elevation 8 clicks and I'm back on (so far!).
If my new upper comes back still out of whack, and I kept it, I bet I'd have to do a lot more windage adjustment than I'd like.
After reading the thread I thought the rail receiver alignment was the issue, not the barrel. I may be reading wrong.
Wouldn't that just be solved by using a carry handle or something to hold them aligned while installing the rail?
I think his barrel is off-center with the rail, but he has to narrow down where the problem lies--I'm betting it's not the rail or nut...I'm betting it's the upper, the upper's threading or barrel.
"A machinist for a very well known company that many people on this board buy from, showed me how to look for crooked extrusions..." -- ARE YOU GONNA TELL US? ;o) I don't even know what an extrusion is...the NSR barrel nut seems easy to make straight, and I'd think if it was gtg, the rail would be gtg.
Robb Jensen
08-28-13, 06:19
When I encounter this issue assembling uppers or installing these long rails two things fix the vast majority of them.
Trueing the front edge of the receiver in front in front of the threads. I use the Brownells tool.
Using a KAC Picatinny rail alignment block for holding the top rail in alignment with the upper receiver while tightening the rail or it's screws (on an NSR).
If the rail uses a USGI type bbl nut many times using another bbl nut will fix it too. Some are truer than others.
When I encounter this issue assembling uppers or installing these long rails two things fix the vast majority of them.
Trueing the front edge of the receiver in front in front of the threads. I use the Brownells tool.
Using a KAC Picatinny rail alignment block for holding the top rail in alignment with the upper receiver while tightening the rail or it's screws (on an NSR).
If the rail uses a USGI type bbl nut many times using another bbl nut will fix it too. Some are truer than others.
I took a Colt 6920 and swapped barrels and uppers with the nsr rail on each. The rail was perfectly centered on the bcm upper with the colt barrel installed. It was off center with the bcm barrel on the colt upper. This narrows it down to the barrel/extension.
BCM asked me to return the whole upper. They've been awesome with communication about this. Any company can and does produce a lemon here and there, it's how they deal with it that counts.
REPORTING back on my BCM 14.5" LW BHF middy:
Just got it back and it appears to be a whole new upper...regardless, everything is as straight as an arrow.
Awesome CS and a 12 day door-to-door turnaround.
Tooth & Nail
08-28-13, 17:39
REPORTING back on my BCM 14.5" LW BHF middy:
Just got it back and it appears to be a whole new upper...regardless, everything is as straight as an arrow.
Awesome CS and a 12 day door-to-door turnaround.
That is great news! I'm glad it worked out well for you, and that BCM turned what could have been an unfortunate experience into something positive. Thank you for the update.
Bcms a great company I'm sure they'll have everyone fixed up pretty quick.I want to use an nsr rail on one of their 20" uppers,hopefully this is just a fluke
UPDATE:
I spoke with a gentleman at BCM who requested that I send the upper and NSR rail to them so they could evaluate the issue. Since I shaved down the FSB, I agreed to buy a low-pro gas block from them and they offered to assemble and test fire the rail and upper free of charge. I added a gunfighter comp to the order as well. I should point out that BCM doesn't typically offer assembly services, so this is a very generous gesture on their part.
I got it back today and it appears to be a brand new barrel and possibly upper as well. The box was loaded with tons of their customary swag.
The barrel and rail are laser straight and look beautiful. BCM's customer service is the industry standard as far as I'm concerned. Hell, I've spent time on the phone with Sony, trying to get a repair authorization for a $50,000 camera and was treated like a hobo. Muchos kudos to BCM.
http://i51.photobucket.com/albums/f392/BiteyMcClaws/20130926_151029_zps3be1e581.jpg~original (http://s51.photobucket.com/user/BiteyMcClaws/media/20130926_151029_zps3be1e581.jpg.html)
WoW! That is awesome. Rifle looks great from this angle.
davestarbuck
10-01-13, 22:20
I built an upper this year that has the same problem, it zeroed with a bunch of right windage. I'm guessing the upper receiver is out of true, but no worries, it's dead on with irons and Aimpoint at 200 yards.
If it will zero, don't worry about it!
I wrote about this a while ago.
Basically, the culprit is most likely your barrel extension or upper receiver.
The dimensions of those areas are not required by spec to be at the level of straightness that you need to ensure that your barrel will be perfectly centered inside a floating tube.
Still, it is not a functional issue, and if you can't get over it you can fix it with some work.
Typos brought to you via Tapatalk and autocorrect.
Obviously sights will be moved off-center to compensate, but will the lateral zero at 100m still be true at 500m? Or will it shift like a side-mounted optic or laser? Lots of angles and math get to me :(
black22rifle
10-05-13, 19:45
Obviously sights will be moved off-center to compensate, but will the lateral zero at 100m still be true at 500m? Or will it shift like a side-mounted optic or laser? Lots of angles and math get to me :(
It should, the sights being off center will center the barrel itself with the target.
Just finished putting mine together. The 13.9" NSR clocked perfectly at 50 lb ft and the end of the rail is nicely centered on the barrel. Just a couple of clicks windage got her zeroed on the keyhole upper I mounted it to. :)
first there
10-16-13, 22:46
Same problem with my bcm upper and 11 inch troy vtac rail. The barrel nut wouldn't time up right with my gas tube just barely off. Shaved the spline down rail was crooked still. Mounted my aimpoint to the rail and upper it straightened out tightend down the bolts. Shoots fine and lines up.
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