Re: magnificaion needed?
I'll second Dave on the 6.5-20X. Great scope, flexible enough to cover most anything you'd use that rifle for.
The 24X is real nice, I used to shoot groundhogs with one on my 22-250. Came to realize that the 6.5-20X could bring them almost as close, but I could also dial it down a little on closer shots (rarely did though), and more importantly if the mirage got too bad.
As for the Mk4 M1 16X, awesome scope. I have one on my LR 308 rifle. Also, a lot of money to justify. For the few hundred dollar difference in price, you might be better off with the 6.5-20X, and put the difference into a trigger job, tuning, AMMO, binos, etc, etc...