ACOG optic & the ar-15/m16s
if your even considering the ACOG series look on the link FIRST.
the ACOG is a proven optic for combat. however it does have some "interesting" features/pitfalls that those who haven't lugged them around in the sand probably don't know about.
the most often versions used are the 4x and the 3.5x and are very well illuminated. these are mostly light weight and very rugged. they weigh in around 10oz or so IIRC. so not much more than a fixed power rifle scope like a weaver k4/k6. other more complex versions weight as much as 30oz--
we tended to favor the lighter ones.
the ACOG series is also known for very short 1.5" (or less) eye relief and a fairly "tight" eye box.
this is because the DOD in their wisdom wanted a scope that kept the nose to the charging handle of the old peeps--
newer versions have up to about 3.3" --however their on the more heavy models.
as much as i like the old TA1s i haven't found myself wanting to buy one. too expensive for me and i ain't one to want to re-live past experiences with USGI shit.
for general survival use you probably better off with a civilian type of scope/optic and spend the savings on more ammo. it is a pretty good piece of kit just the expense and the USGI "oddness" of it still puts me off a little.
if they were going for "worth" i would pick one up. @ mall ninja prices--not to much--LOL