RE: 243 or 6mm for deer
Actually, there isnt a dimes worth of difference between the two in the speed arena. You can see 100 fps difference between two rifles of the same caliber, shooting the same ammunition. If you lean toward the 6mm Remington, make sure you check the twist. Early 6mms would not stabilize heavy bullets well. The 243 was designed from day one to handle 100 grain bullets.