Always refer to your loading manuals. Maximum oal length for a magazine in 243 winchester is 2.710. Hornady's manual will tell you they got their best loads at 2.630 oal for 95 - 100gr bullets. Measure your magazine inside length. Usually .005 to .010 under works well. Hope that helps. Capt kurt
It really depends on your magazine length and design. With most rifles if you can push a round squarely all the way to the bottom of your magazine without it binding it should work. This is a trial and error situation for you and your individual rifle.