Not necessarily C&R and not necessarily milsurp, but don't forget about .22. I'll bet that I've put more .22LR rounds downrange than all of my other calibers combined. You can get a brick of bulk ammo for about the same price as 20 good .30-06 rounds.
Oh, and if you reload (or even better, if you reload and cast), almost any caliber starts getting cheap. I bought 400 rounds of HXP .30-06 from CMP a couple of years ago and I've been reloading that brass ever since...keeping in mind my first paragraph.
Well we don't rent pigs and I figure it's better to say it right out front because a man that does like to rent pigs is... he's hard to stop - Gus McCrae