It really depends on what you're going to use this rifle for. Your 30-06 covers a huge range as a hunting rifle and is going to be very hard to beat! The 7mm Rem. Mag. is going to shoot a little flatter and retain a little more down range energy then your 30-06. Unless you're going to be shooting past 300-350 yards you'll never know the difference between the two, and even past this range,its not thatbig of a deal.

"Caliber wise" (bullet diameter)if you're looking for something in between your 243 Win.and 30-06 Spr.that would be a 270 Win.which is very close in performanceto your 30-06. The 270 Win. will shot a tad flatter then your 30-06, but again you're probably not going to be able to tell the difference inactually hunting conditions.

Some other cartridges to consider thatare in between your 243 Win. and 30-06 Spr. arethe 25-06 Rem., 257 Roberts,260 Rem.or 6.5x55 Swedish.

If you're just looking for a rifle to shoot, look at a 223 Rem. or something like that.