Hi, I have a Colt CAR-A3 HBAR ELITE that I recently put a Daniel Defense M4A1 RIS-2 on. I also installed an Adams Arms piston kit. I had to modify the rail slightly to make it all work together. But, in the end, it looks and functions very well. That's what started this: I have another AR that I built 3 years ago. I built it with an AA piston system that I am happy with. I was told, at the time, that the only rail that would work with it is the Samson Evolution 9 rail. I'm not so happy with the rail. It clamps onto two pieces of metal that slip over the barrel nut. I don't feel it is as rock solid as the DD rail on my Colt. I got the DD rail to work flawlessly with the piston once, and I'm sure I can do it again with a little advice.... So, I need to know the length of a MK18 RIS-2 from the face at the upper receiver to the face at the gas block. The website says the overall length of the rail is 9.5". But, I'm hoping that includes the bolt plate and any overhang at the upper receiver. Thanks for any information!!!