I built a 243AI 7-8 years ago and wanted it to be my favorite deer rifle. I love the rifle and I love the cartridge, but ended up deciding it's not a deer rifle. That's partially my fault as I committed to the 105gr AMAX (discontinued but I stocked up 1K), and learned that's NOT a deer bullet at those velocities. Had a bad experience on an antelope, shot it twice in the shoulder at 400 yards and neither penetrated. Decided I wanted something more forgiving than even working up a different bullet.
I built a 6.5-06AI and worked up loads for both the 140gr Accubond and 143gr ELD-X. An old, well-used R700 action with a McGowen barrel in a McMillan Game Scout stock with one of the last Jewell triggers. Last year I did crop damage permits on the family farm in Michigan, 5 deer from 200 to 720 yards. The 140AB performed as advertised, penetrating reliably. However in this setting, with the deer in tall beans, any sort of run was a liability for recovery. I needed them to go down faster. This year I switched to the 143gr ELD-X and again shot 5 deer from 80 to 465 yards. The results were superb. The first two at 430 yards ran 30 yards max, both angling chest shots. One through the front of the chest at an angle at 300 was DRT. The 80yd shot was diagonal through the front of the chest, DRT. 465yd quartering shot, DRT. Every bullet exited at least the lead except 1, 2 bullets recovered after passing through off side shoulder (1 complete, 1 jacket only). Mushroomed without fragmentation. The 80 yd shot I expected it to blow up but it passed through 18-22 inches of deer and exited.
The 6.5-06AI with the 143gr ELD-X at 3100fps exhibits slightly better ballistics than my 300WM with 212gr ELD-X with much less recoil and I was dialing in far less MOA than my friend's 270 and 6.5CM. I run a Griffin dual port brake with Explorr suppressor, the rifle is just a dream to shoot. I could almost (not quite) spot shots clamped in a tripod.