There's always some variation in numbers from various sources. That's why the number I used were linked to their source. If you don't like those numbers, go complain to those webbies, not to me. I merely used them to illustrate a point, which I think I did quite adequately (even assuming weight of various M1 versions was not 100% correct, this does not invalidate the argument, namely that metric and short tons have been confused by some).
I am perfectly aware of the role of GD in the development if the K1 and I fail to see how GD having the primary contract explains anything about weighs. However, if K1 weighs 51 short tons, as you suggest, then that is only about 46,000 kg and K1A1 about 49,000 kg. How come I find no sources online that give that number (incl. professional sites like army-technology, armada etc)? Can you point me to some credible ones?
Read this
http://www.historyofwar.org/articles/weapons_hyundaik1.html
It claims combat weight (which is what we're comparing): 51,100kg
It's sources are: Foss, Christopher.
Jane's Main Battle Tanks, 2nd Edition, Jane's Publishing Company Ltd, London, 1986.
Foss, Christopher. Jane's Tank Recognition Guide, HarperCollins, Glasgow, 1996.
(gee, same author of which I have a 1978 german language edition book, which puts XM-1 at 52,6 metric tons i.e. 52,616 kg)
Have a look at
www.army-technology.com: Is the latest M1A2 version (69.54 ton) really that much heavier than the latest Merkava 4 (65 ton), the latest Chally 2 (62,5 ton) and the latest Leo2 (62 metric ton) ? Or does 69,54x0.907=63 ton sound more plausible? Is K1A1 (54,5 ton) really in the same weight class as T-90S (46,5 ton), as you suggest?