Re: K-16 upper
I purchased a K-16 a couple years back. I wanted a varmint rifle and already had 2 other AR's so I thought I would stick with the AR platform. Saw the K-16, 16" heavy barrel, full floated fore end, etc. Couldn't pass on the price and after doing some research, supposed to have good barrels, I purchased it. It shoots sub- moa, functions flawlessy, fit and finish are good, no problems fitting after market parts. I wouldn't hesitate to recommend for your intended purposes. It is a great value.
As far as rifles being mil-spec, I don't think mil-spec is the end all be all. The AR-10 platform has no mil-specs, so they must all be undependable and junk right? Even though the military (U.S., U.K.) is contracting for them?