In reference to "bullet failures" with the .243; My failures have been with:
1. Speer 105gr "HotCor" sptz. 410yd shot hit lungs mid torso. Pin prick entry wound, 1/4" exit wound. Carcass found 3days later after turkey vultures found it first.
2. Hornady 100gr BtSpt "Interlok"; Forward raking torso shot, deer fell to ground, sparse blood trail, deer traveled over 500yds till blood trail was lost. Never located deer; shot distance was 30yds. Deer trotting away after scenting me.
3. Hornady 100gr RN "Interlok"; 25yd downward raking shot from tree-stand. Bullet impacted just under spine raking downward just behind shoulder on broadside shot. Deer fell at shot, jump up and ran with tail down out of sight. Because entry wound was above mid-line of torso, no blood trail. Just brown hair/blood blown out of entry wound. Deer never found.
4. Sierra 100gr BTSpt (before they were call "GameKings" in early 1980's) chrono'd 3,000fps load (IMR4350) from 24" bbl Rem. 700 varminter; Range-estimate 390yds (paced by shooter). Bullet seen to impact behind shoulder, below spine w/broadside shot. Deer found 5days later, Boone $ Crockett head (non-typical) Harris Co. Ga. Property now owned by Jeff Foxworth/Bill Jordan (Realtree Industries). Pin hole entry, pin-hole exit, one rib broken prior to exit. Shooter "retired" the .243 and has since used a .270, later a .300WSM (rifle was anniversary gift from wife....).
5. 100gr Nosler Partition (Federal factory load). 25yd shot, to lungs/liver. Deer ran 500yds and collapsed under other hunters stand on adjacent lease. Shooter was detained by "witness" for prosecution for "tresspass/hunting w/o permission. I declined to prosecute as "shooter" showed me the "back trail" of blood to his stand; and left his rifle at property line leaned up against tree.
I'm not including all the "blow ups" I've seen with "poachers" using the 80gr and lighter bullets. Or, those shot at night across fields/powerline row's; ect.
Sorry, my "ambivalence" towards the .243 is from personal observation and experience over a 25yr career in Conservation Enforcement and 40yrs of deer hunting. I still have a .243 and it's very accurate, and I killed the only deer I shot last year with it. (100gr Privi Partisan Semi-Pt Spt. 164yds, from my kitchen window (lased). Broadside heart shot, deer ran 25yds.... pin prick entry, 3/4" exit wound... Typical of my experience with most "deer" weight bullets in the .243. (41.5gr IMR4350, chrono's ~2,950fps).
(shot placement, shot placement, shot placement...).
But; I've had "failures" with the 7mm08, but have been limited to failure to expand on "trick" bullets (Hornady 140gr SST's). Only deer of 5 shot with bullets from that lot # was shot downward from tree stand through the spine. Bullet at ~2,750fps impact velocity still failed to expand... I prefer Sierra's and Rem. CorLokts.....