How about 'after-market' M-16/AR-15 magazines for said guns?
By definition, any magazine not purchased from the manufacturer of the rifle would be after market. We could get in to a philosophical discussion on who actually made the rifle as opposed to who merely assembled it, but that is for the birds. I haven't had a lot of experience with different magazines, but the 3 I have that have seen the Iraq desert seem to work still, the CMMG mags I have work well, though I have seen one that acted funny in a friend's del-ton kit; and PMags are great, but don't seem to "do it better" than the other mags I've used.
That being said, the AR has the cheapest "flawless every time" mags of any rifle available. $10-$25 from cheapest good mag to most expensive good mag is unheard-of in any other rifle that I can think of.
It seems like most of the American Gun makers now have an AR-15 Style rifle/carbine.
I can think of two, if you define American Gun Makers as any general gun manufacturer in the US, which is Remmy and S&W. They just happen to be the two companies that hopped on the gravy train first. I'd be willing to bet Winchester will follow, like they did with the Laredo after the Sendero. Basically, if you figure that there are only 3-5 American Gun Makers in the US, then yes your observation is correct. I figure there are more, however, and that only 2 have brought on an AR line.
Most AR-15 rifle renditions seem pretty generic for the most part
How so, because they look alike? That's like saying Remington, Winchester and Savage are all pretty generic. True the differences between Bushmaster, DPMS and Colt may seem more miniscule when you look at them, but there are many machine companies that make the parts and many barrel manufacturers that make the barrels; all of which have different specs and use different materials. It's a lot more complicated than that, but you get the idea.
