They still make both the 16 and 20 inch models, but only one barrel profile of each. There are no longer a standard (heavy) and light versions of each length. Availability of 16 vs 20 has always gone back and forth as to which one is easy to find. 2 years ago finding a 16 inch was nearly impossible, and 20's were everywhere.
I bought a used 20" heavy at my local Gander Mountain last month for $900.00. It had already had the muzzle threaded and included 3 mags and a thread protector. I did not hesitate on that deal. The rifle was in unfired/new condition
i just Bought a slightly used FNAR 20 inch light barrel. Great rifle and it cycles everything perfectly, I have only tried Federal Deer Thugs 165 grain soft points, Freedom Munitions 150 grain which are reman's, Winchester 168 gr match and a bunch of hand loads my brother in law cooked up. It likes 165-168 gr best no matter what, but is acceptable with 150 grain as well. A friend had 16 rnds of Federal gold match 168 grain. It was noticeably the best so far but the 168 gr hand loads from my BIL were fired in a 17 mph wind and may have been as good or better. With all the above mentioned all fired acceptably and cycled well. Had only one fte in 210+ rounds fired. 2 inch worst down to 3/4 at 100. To be realistic it is more accurate than my friends DPMS 308, also lighter. About the only thing I would trade for it would be an AR in 308 that I could build on. I bought it for hog hunting but have never had a chance to go yet. BTW glass: Trijacon Accupoint 3X9X40 green triangle, my favorite glass in this price range. Love it so far