Here is another mini/micro dot sight that might be of interest...
http://www.vortextactical.com/product/vortex-sparc-red-dot-scope
the SPARC sells with a modular mount( risers/shims) that allow it to be used on different rifles, and also sells with a 2X magnifier.
Night vision compatible, and also has settings allowing it to be used in mid day sun.
* 2MOA dot
* 5.2oz
* 3in total length.
* Vortex lifetime transferable warranty.
* 4 different mounting heights (.725in/.875in/1.425in/1.575in)
* Battery type : CR-2354
* Battery life: (6 hr auto shutdown feature)
Normal mode of operation = 120hrs at maximum to 3400hrs minimum.
NV mode = 4200 hrs max to 4600 hrs min.
* Operating temperature rating: -40 to 140 drgrees F.
Even sports an ARD, but will cost extra for it.
A good friend of mine has recently decided on the SPARC, and plans to set it up on his wife's M1 Carbine/Ultimak rig, but neither of us have any hands on with one as of yet.
Regarding the M8 rail: The rail itself is aluminum, but the bbl mounting brackets are of stainless steel, so I'm fairly certain it would weigh more than the split rail ARMS 18, but it's best feature is allowing for co-witness.
One issue I might run into with this sight mounted on the ARMS is that of ejecting brass smacking the sight on their way out. No issues with the Ultimak, as it should keep any optic mounted to it away from the action.
A few pics of the split rail ARMS 18 mount for better clarification as to what I am referring to as a possible issue....
11B