ok, just because my wife says I would argue with God
I googled some info
http://www.chuckhawks.com/rifle_ballistics_table.htmI realize there are differences in ballistics data, depending on powder, bullet weight, barrel length, etc, so I just grabbed one for an example.
The 300win mag is a long distance cartridge..300 Win. Mag. (180 Sp) MV - 2960fps, V @ 200 yds - 2540fps, ME (ft lb)3501ft lb, E @ 200 yds - 2578ft lb
Target shooting? ok 1,000 yard shot kill some paper. Hunting? I personnally wouldnt take a shot longer that 300 yards. I dont remember the math but at 1,000 yards I doubt there is very much kinetic energy left, (maybe 700lbs give or take) plenty to kill with but then you'd have to drill'em in heart or the head.
You can use a 223 on white tail in tx..223 Rem. (55 Sp) MV 3240fps, V @ 200 yds 2304fps, ME (ft lb) 1282ft lb, E @ 200 yds 648ft lb
.308 Win. (180 Sp) MV - 2620, V @ 200 yds - 2198, ME (ft lb) 2743, E @ 200 yds 1930
.223 would require better shot placement and luck. Luck and I dont get along well, I would rather use a .308