Rail lock up/ mount up question.

[Dos Cylindros]

Okay, here is the question. I am in the market for a new upper and am trying to decide between two different uppers with two different rail systems. I have my reasons for wanting each one, but my decision will boil down to the most secure mounting solution. Which one of these rail systems has the best "lock up" to the receiver to resist rotation?

KAC URX II (rifle length)

DD Lite rail 9.0

DD Omega X 9.0

Right now I am leaning toward the KAC but am unsure of how secure it is compared to the DD units. My current upper has the DD lite, so I know that is solid and secure but was curious about how the other two compare. Gun will be used for tactical entries at work and HD/Training.

Thanks for any imput.

[Belmont31R]

None of them have anti-rotation tabs....the DD RIS II does but the Lite does not.



The URX rail is screw onto the upper, and then the barrel nut keeps the barrel in place. Its unlikely the rail will rotate.


The DD Lite is kind of the opposite in that the barrel nut is put in place with the "collar" behind the nut. The rail is then put on, and the collar and rail are screw together. The only thing keeping the rail from turning is the force between the collar and rail via the screws.


If you want a rail that has actual anti-rotation tabs look at LaRue or the DD RIS II otherwise the only thing keeping the rail from spinning on the ones you mentioned is tension.

[Dos Cylindros]

Okay, thanks Belmont. I appreciate the info.