I am planning to put a dot sight on my AR mounted in the forward position on an ARMS #39 bi level mount. First, can either sight be set up for co-witness, and is one better in this forward position than the other? It seems the Eo might be better since it is basically a flat surface as opposed to the aimpoint being a tube. If either can be co-witnessed, does anyone know which mount to use? I don't want to waste money buying mounts that don't work.

TIA

I don't own either - but I've been researching the same issue.

General consensus is that the Aimpoint cowitnesses great with the ARMS #39, but the EOTech sits too high.  You need the PRI Gooseneck mount for the EOTech if you want it to cowitness.

I am sure others can give you more specifics.

For use w/ the ARMS #39A2 mount the Aimpoint ML or ML2 will co-witness with just the ARMS #22M68 mount, (no spacer necessary).

For the EOTech to co-witness it will require a different approach. (as the EOTech needs to be mounted at the "flat-top" height inorder to "co-witness")

1. you can use a KAC RIS, w/ EOTech mounted direct to it.
2. there's a maker of an adjustable version (PRI has one) of the #39A2 type mount, which the EOTech can be mounted to directly, that can be adjusted to the correct co-witness height.
3. you can use the cheaper Fobus "railed" handguards, (but NOTE: these do NOT provide as soild a platform and may shift POI with use)
4. ARMS makes a S.I.R. sysytem, the #50 or 51 IIRC that has a "two" leveled rail, with the over the handgurad area "AT THE PROPER HEIGHT" for co-witness EOTech mounting.

Hope this helps, remember the Aimpoints need the ARMS #22M68 with the spacer to mount directly on the flat-top, and the the "slanted or cantilever" spacer has become a popular option as opposed to the standard square one, as it postions the Aimpoint further foward.

Good Luck,
Mike

Thanks for the info guys. That answers a lot for me. I would asume that if there are that many people mounting the ML series Aimpoints inthe forward position, that there are litttle to no issues with sighting thru them.