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Posted: 2/14/2015 9:23:30 PM EDT
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So I instaled an ras I recieved from KAC, and i made sure the locking teeth was under
the barrel nut and the gas tube was between the teeth. Its locked up solid and no movement at all. But.... the problem is, I noticed that the top rail of the ras is higher than the upper of my rifle(colt 6920 btw). So my question is, is this normal or is the rail out of spec? I call Knights, no answer, obviously its the weekend and they are probably closed..... No pic yet.Ill try to get some decent iphone pics if needed. |
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Yes I had this issue with my new kac ras for the rifle and carbine. It's suppose to be even. For me with my rifle I ended up hurting myself the first time putting it in right. It was very painful so be careful.
You put the top rail in first by the front end handguard ring. Make sure the guide "clicks" in to the delta/gas tube. Sometimes a little pressure helps but I found completely undoing the screw out helps in making sure it seats in correctly. The bottom rail is easy to fit once you get the top. Edit: Another good advice I have is to make sure the butt of the rifle is on the ground. You can "cup" the delta ring and apply pressure when you're setting. Putting the rifle on the butt will aid in delta ring pressure, the gas tube guide setting down by gavity, and making sure the rails drop into the delta ring. So be sure to do that. Again I injured myself on my rifle. My hand slipped from the delta at the same time the rails went in and my thumb hit the side really hard. So be very careful in doing this. |
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PICS!!!! Its kinda hard to tell, but when I look at the rifle there is a height difference.
I thought maybe it is just my eyes playing tricks on me but when i bridged my aimpoint to see, the ras was higher than the flat top beacause the aimpoint was at and angle. 
The gap between the upper. could be me but I swear there is a height difference. 
Front tab is under the handguard cap. |
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Quoted: PICS!!!! Its kinda hard to tell, but when I look at the rifle there is a height difference. I thought maybe it is just my eyes playing tricks on me but when i bridged my aimpoint to see, the ras was higher than the flat top beacause the aimpoint was at and angle. http://i36.photobucket.com/albums/e14/NathanTribes/Mobile%20Uploads/photo%201_zpsbdyk7ivm.jpg The gap between the upper. could be me but I swear there is a height difference. http://i36.photobucket.com/albums/e14/NathanTribes/Mobile%20Uploads/photo%202_zpstnbbtjwv.jpg Front tab is under the handguard cap. |
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I just checked all 3 of my KAC rails with a machinists rule. All of mine sit on the same plane as the rail on the upper.
For fun, I took them all off (1 M4 RAS, and 2 M5's), and re-installed them. In 2 cases, I was able to duplicate the slight misalignment between the rail and the upper. I don't think the clamp teeth of your rail is properly engaged with the barrel nut. I had to take mine off a couple of times and ensure it was seated. Once it was fully seated, the rail heights matched perfectly. I think you need to take it off and try again. |
I know it isnt fully tightened, but in these pics the whole thing is together.
After further inspection... it sill looks uneven but every thing is rock solid. I might just be crazy.... 
However I will check to see if the teeth are fully under the barrel nut again. |
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Lightly tap on the upper rail and tighten the locking tab with two fingers on the screwdriver. That should settle it in. It looks ok, the delta ring would be off more than that if the tab was on top of the nut.
Fun RAS story of the morning: I was once distracted by a (smokin' hot) female coworker and managed to install the upper rail of a RAS into a brand new Colt with all the meat of my 1st finger on my right hand between the rail and the barrel nut. 
Was quite painful and took two guys to get the rail back off. I had a barrel nut lookin' blood blister on my finger for about a week and a half. 
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