A few weeks ago, a reader emailed to ask for an article regarding preferred Aimpoint mounting locations on carbines. I have always done what just seemed right to me and had never put much thought into it. But apparently there was some method behind my madness, so here are my thoughts on the topic. Note that much of this is based on personal preference, so you may want to adjust to your needs.
The first point of consideration is whether I am mounting a full size Comp M68 or a Micro. The Micro is an excellent evolution of the sight and offers outstanding battery life, durability, in a lighter and more compact package than the M68. However, the viewing window is indeed smaller which, to me, changes some things as to how my eye picks up the dot when I mount the rifle.
I prefer to mount the M68 as far forward on the receiver as possible. If I plan to use a magnifier, I prefer to use a cantilever mount like the LaRue LT129 Cantilever Aimpoint Mount. The viewing area is large and easy to pick up. I don’t like mounting further forward than the end of the receiver since you can get loss of zero if your rail is not monolithic with the receiver. Also, the optic is now so far forward from your face the dot can be harder to pick up. Add to the fact that mounting accessories at the muzzle end of the gun makes it harder to hold for an extended period of time. Likewise, I don’t recommend mounting the M68 too far back as it precludes the ability to mount a 3X magnifier behind it. Even if you have the rail space, some folks mount the M68 far enough back that the magnifier is just about jammed into your eyeball.
The T-1, T-2 and H-series optics are my preference when I’m trying to set up the lightest, handiest guns possible. One of the downsides for me is that the viewing window is smaller than that of its bigger brother. Theoretically, this is not a problem as the RDS is not magnified and can be used both eyes open. However, the smaller window does mean you have less margin for error when picking up the dot because if your head/eye shifts beyond a certain range, the dot is no longer visible. What I like to do is bring the Micro just a little bit back toward my eye, which effectively increases the apparent window size. Just be sure to leave space for a magnifier, if that is a piece of gear you will be using.