Did BCM make a mistake on my rail?

[Colorado S14]

Clickbait title aside I do have a question regarding my beautiful new MCMR.15 rail. The picatinny location markings on my rail start at T14 which on any upper I own would cause a double T14 situation. My Midwest rail starts at T16 and I would think that is the correct standard, thoughts?

Updated note: The rifle is not assembled, so the gap is not a reflection of the rail or upper fit, I simply put them together for an illustration.
New BCM rail:
51150
51151

Midwest for comparison:
51152

[Iraqgunz]

You could try contacting them and asking.

[sidewaysil80]

For what its worth the picatinny on my colt upper receiver sits ever so lightly higher than the MI rail that it came with. It’s the Colt “Combat Unit Carbine”. Not sure who shit the bed on the that but it doesn't effect anything just annyoys me from an aesthetic point of view.

As far as the T Markings thats your uppers fault. Most receiver markings stop at “T 12”, have a blank slot, then have a small section w/ no slot. Just like the Spikes you posted. The receiver you posted with the BCM rail doesn’t have that “blank” slot and is numbered to “T 14”, so it appears your upper receiver is not mil-spec and is the culprit. Which also wouldn’t surprise me if the height issue was as a result of the upper receiver as well.

[GH41]

Clickbait title aside I do have a question regarding my beautiful new MCMR.15 rail. The picatinny location markings on my rail start at T14 which on any upper I own would cause a double T14 situation. My Midwest rail starts at T16 and I would think that is the correct standard, thoughts?

Is the difference in height between the receiver and rail as pronounced as it looks in picture #2?

[jackblack73]

All of my rifles (all different brand rails) sit slightly lower than the rail on the receiver. Before the rail is tightened down they're level, but when you start tightening the rail deforms slightly. Doesn't bother me at all.

[GH41]

All of my rifles (all different brand rails) sit slightly lower than the rail on the receiver. Before the rail is tightened down they're level, but when you start tightening the rail deforms slightly. Doesn't bother me at all.

Are any of your rails BCM? Traditional rails with bottom clamp screws deform. BCM rails that clamp at the top do not. That is the beauty of their system.. The nut doesn't have to be timed and the rail doesn't deform.

[GH41]

I keep forgetting to answer the OP's question.. The forward most mark on a BCM receiver is T13.

[GH41]

I keep forgetting to answer the OP's question.. The forward most mark on a BCM receiver is T12 making the last slot T13.
https://i.imgur.com/CRFPGrJ.jpg

[Nightstalker865]

As others have pointed out, it looks like the issue is with the upper and not the rail. At a glance it doesn’t look like a BCM upper. Who makes it?


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[jwfuhrman]

As others have pointed out, it looks like the issue is with the upper and not the rail. At a glance it doesn’t look like a BCM upper. Who makes it?




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Agreed, looking at the picture in question, the upper is NOT a BCM upper. I don't even know what brand upper it is as I've never seen relief cuts down the center length wise on any known QUALITY manufacturers upper receiver.

[ballen0032]

It appears to be an Aero M4E1 enhanced upper. As for the rail not being level with the upper, if you look close in pic#2 I see the barrel nut threads. I don't think he has the rail over a barrel
nut, causing misalignment.

[Colorado S14]

I created some confusion (I added a note to my original post), the rifle is not assembled, so the gap is not a reflection of the handguard or upper fit, I simply put them together for an illustration. I do not anticipate any fit issues.

It was just interesting the markings on the handguard, it just seems to me that on either my Spikes or Aero uppers a T16 marking should be the first on the handguard and not T14. I don't plan to even contact BCM, I am sure there is a reason for doing it the way they do and on my gun it will be mostly obscured by an optic anyway. The HG is beautiful by the way.

[sidewaysil80]

it just seems to me that on either my Spikes or Aero uppers a T16 marking should be the first on the handguard and not T14.

The correct (ala Mil-spec) is that the T-13 (unmarked) is the last slot on the picatinny top rail. Notice how the area above T-13 COULD fit another slot, but it doesn't. I don't know why it doesn't, but per the TDP it is uncut; thus T-13 is the last slot. See below for correct/mil-spec upper receiver...

https://picturearchive.gunauction.com/1121145810/9945149/5a819ab72e4f94696377f9570b6eebd2.jpg

https://cdn2.bigcommerce.com/server5500/47d11/products/812/images/2360/M4_upper_right__45034.1469945779.1280.1280.jpg?c=2

[jackblack73]

Are any of your rails BCM? Traditional rails with bottom clamp screws deform. BCM rails that clamp at the top do not. That is the beauty of their system.. The nut doesn't have to be timed and the rail doesn't deform.
One is a BCM, and it sits below the receiver's rail the least. It barely does so, in fact. I shouldn't have included that rifle when I said they're level before they're tightened, because it's a factory BCM upper and I never saw it prior to being tightened.

[stascom]

I've seen a few "boutique" ARs with misaligned rails. I would ask DD to fix it.

[JSantoro]

Trying to get DD to fix a non-DD product/assembly seems like an odd piece of advice.

[RAM Engineer]

For what its worth the picatinny on my colt upper receiver sits ever so lightly higher than the MI rail that it came with. It’s the Colt “Combat Unit Carbine”. Not sure who shit the bed on the that but it doesn't effect anything just annyoys me from an aesthetic point of view.

Every Colt I've seen with an Centurion Rail (not MI) has had that issue. CCU's have Centurion Rails, not MI.