It is my belief that a general purpose carbine (in this instance, an AR-15) should have a magnified optical sight.
Whilst a low power variable magnification optic would obviously be a good choice, as it could be adapted to a wide variety of circumstances, finding one of sufficient quality tends to be an expensive affair - especially over here. There are, of course, cheap scopes too (Vortex Strike Eagle 1-6x leaps to mind), but their quality and reliability seem a bit suspect. Since fixed magnification scopes have an inherently simpler construction, it seems to me that one of those, with the same price point as a low power variable, ought to be a more reliable choice with better glass. And looking over reviews of cheap scopes such as the Primary Arms prism scopes, it certainly seems that they can take a bit of a beating and seem to have markedly clearer glass than variable scopes of similar price.
At proper rifle ranges, a fixed magnification should not of course be an issue. I am, however, wondering how difficult would using a fixed magnification sight at close ranges be? Most reviews and such I've found have heavily focused on using these scopes at ranges they are most suitable in, skipping pretty much entirely over the topic of what if one needs to shoot something at a really short range.
I am hoping some of you ladies and gentlemen have spent enough time with fixed magnification sights to be able to give me some idea of how large a performance hit would a regular bloke take when using a sight like this in close range applications, and whether or not one could train to a reasonable standard of proficiency with a sighting system like this, with a reasonable expenditure of time and effort.
Thank you all for your help.