Maybe the South Texas and Northwest North Carolina markets are a little different. Around here, if you had 2 identical rifles for sale, one in .243 and one in 6mm, you would be able to get about $100 more for the 6mm, simply because of the non-availability of a new 6mm. Also alot of people know the 6mm is ballistically superior. I realize the .243 ammo is a little more common but there's no shortage of 6mm ammo either. Its easy to find brass to reload since 7x57 or .257 roberts brass can be re-sized to work. I know several people in my neck of the woods that deer hunt exclusively with a 6mm rem. There are always want ads in the classifieds with people wanting to buy a 6mm rem rifle. I own two myself, the M77 as you mentioned and an older Remington 700 varmint. If they are so cheap in south Texas I need to make a trip down there and buy up some 6mm rifles to re-sale up here. Wanna sell yours?
What other caliber would you like me to pick? They would all be more useful for hunting than a .22lr
Blessed be the Lord my strength which teacheth my hands to war, and my fingers to fight -Psalm 144:1, KJV, a Psalm of David