I LOVE mine, but DevL is exactly right. It's not intended to be a low-light optic.
I worked around that in a half-assed way by installing a Surefire forend, and use it to dispatch skunks raiding my wife's tomato garden at night. It has served very well in that capacity.
It has a beautiful [b]bright[/b] reticle, is built like a tank, and is extremely forgiving in terms of eye relief. Overall I'm very happy with mine and would gladly buy another if I needed to replace this one.
[img]http://home.comcast.net/~cjan99999/HBAR_leupold.JPG[/img]
[img]http://home.comcast.net/~cjan99999/Hbar_m4.jpg[/img]
[img]http://home.comcast.net/~cjan99999/scope2.jpg[/img]
Good luck with yours. It will be a great addition to either of your rifles.
EDIT: It's pretty slick on my M4 carbine as well.
[img]http://home.comcast.net/~cjan99999/M4_Scope.jpg[/img]