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Posted: 11/4/2005 5:50:35 PM EDT
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I noticed that the picatinny rail on my CMT upper is different from other CMT upper rails that I have seen. Just currious if there is a reason for the difference or if it's out of spec? Here are a couple pics of my CMT upper:   Here's another CMT upper where the rear of the rail is different. The edge of the rail extends back to the groove for the charging handle latch.  |
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Interesting...I've been paying attention to other photos around here and I've seen RRA uppers in BOTH configurations as well (But then again, doesn't CMT make uppers for RRA too?). I'm just currious if there's some strange reason for this...someone around here has to know. |
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Mine that I just got in doesnt extend that far back. My only logical explanation would be that it offers more rail room, and that isnt a bad thing. And I wouldnt jump the gun and say they could be a craptart, whats wrong with a little bit more rail? Interesting though. |
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There is nothing wrong with more rail...I think he was referring to the version with less rail as being a "craptart." I did notice that my Troy BUIS now "hangs over" the back of the rail in a sense. Doesn't seem like it will be a problem, but I'm beginning to wonder if this is simply an out of spec upper or a purposeful change. |
The two flat tops at my house, one CMT made Rock River, and one sold under the CMT name, both look like the unit in the lower pic (w/the green background). But my reaction to the original question is "So What"?. Both these pieces are perfectly functional, and I can find no reason to downrate either one. That being said, I'm puzzled by the reason for anyone's concern. 
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What is the big deal? Does it weaken the part or impair function? It is cosmetically acceptable to me. It is not like there is a perfect AR pattern out there that every artistic manufacturer aspires to craft. Gee, you should see the flattop I hacked out of a forging. |
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Cosmetic machining aside, the only way to see if the rail is in spec is to measure it. The picatinny rail has a spec for sure, but I'm not sure if what you have highlighted has a spec and even if it does, does it make any difference. The rail is what stuff mounts to, not the rear of the receiver. FWIW. |
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My question isn't about cosmetics--the upper looks great. I'm just curious why there are differences in the length of the "mountable" area. It doesn't make a huge difference, but it also doesn't seem to be the correct length for mounting my BUIS. Have a look at the differences: Here is my Troy BUIS mounted to my RRA upper that has the additional "mountable" area lacked by the CMT upper. Things look like they should and the rail provides just enough room.  Now look at my Troy BUIS mounted on my CMT upper. There isn't enough "mountable" area and the sight hangs off the back. Sure, its not going to fall off the upper, but why would CMT do this?  
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That may be the case, but I think it's pretty clear that CMT has made BOTH versions as the pictures show. I don't necessarily think it's a defect either, but I'd like to know why there is variation in how they cut their rails. |
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I just had a crazy idea. Both my friend and I have CMT upper with the shorter rails, and each of us also have M4-cut extended feed ramps on our uppers. And this other person I know has a CMT reciever without M4 cuts and his has the extended rail space. Can anyone out there confirm if their version (either with M4 cuts or not), has the extended or shorter rail space? It would be weird if every CMT upper with M4 cuts had the shorter rail space. Just food for thought...... |
I just grabbed a current production A3 and M4. The M4 rail is extended. C4 
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Well there went that theory. 
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