I have a stainless Ranch Rifle mini I've had for about 20 years. Not the most accurate rifle I have, but I have great faith in it going bang when needed. I have an AR and other stuff, but the mini-14 is the one I keep loaded in the unlikely event some outside work is needed. 50 yards would be a long shot here in the woods, and I have a 2 & 1/2 x "shotgun" scope on it with a heavy duplex reticle. Suits me.

Since development began on the mini-14 in 1967, the AR was certainly around; but not the sure thing it has become, so I can see why it wasn't developed for an AR magazine.