zstephens, I've owned quite a few ACOGs, ranging from the little 1.5Xs to the 4Xs. One thing that I know is that you really can't read the specs and expect to know how the scope is actually going to work for you.
On some models, like the 4Xs, they spec the scope as having something around 1.5" of eye relief and, in my experience, there is a pretty narrow range of distance that your eye has to be from the eye piece to get a clear view through the scope. Many years ago, I tried a couple of 4Xs, sold them and decided that I just didn't like ACOGs.
Well, years after that, a local gun shop started stocking ACOGs and I was able to try many of them. The 4Xs were what I remembered them to be. The funny thing is that the specs seem to mean different things for different lines of ACOGs. For the 4Xs, eye relief meant that your eye had to be right around 1.5" or so from the eye piece to see through the scope; but for the lower magnification scopes, it seemed that the eye relief spec meant more like the minimum distance that your eye had to be from the scope before you could see through it.
With the 3.5X models, the spec'd eye relief is still short at 2.4" or so, but the range of distance that your eye can be from the scope is more forgiving, so you could have your eye anywhere from 2.4 to maybe 3.5" from the eye piece and see through the scope.
Another example is the little 3X model. It's eye relief is spec'd at being pretty short too. Something like 1.5" as well, but in use, the actual eye relief needed to be able to see through the scope is pretty darned forgiving. I mean, really forgiving. The only reason I got away from the 3X ACOGs, was in favor of the Sightron SII Big Sky scopes which weren't much bigger but offer a variable magnification range of 1.5-5X, with better glass and a wider field of view.
A further example is the little TA44S-10, 1.5X. It's eye relief is spec'd at 2.4", but in use, the range of distance that your eye can be from the eye piece is so broad that even considering the eye relief spec isn't needed. In fact, due to astigmatism, I've abandoned using red dots sights all together, in favor the 1.5X ACOGs. I run and use them just like red dots, without consideration for having to have my eye in just the right place.
I can't speak for the higher magnification ACOGs. For my uses, the 2.5-10X32 Nightforce scopes were more flexible, so I went that route.
In the end, my point is that you should check them out before you buy; or at the least, buy from a retailer that will let you return it, if you don't like it.
ACOGs are pretty specialized optics and, although they carry a very high "cool" factor, they aren't for everybody. The main reason that I've never been a fan of BDC reticles is that they are dependent upon load specifics to work well, or well enough for me. I prefer something along the lines of a reticle with either MOA or mil hash marks for purposes of ranging and holdovers.
