Seems to me that if a bullet comes apart in flight, that there was tremendous damage done to the bullet as is traveled down the bore. Increased twist drastically changes bullet rpm. The 30-06 probably had 1-10 twist or maybe 1-12. Some are shooting much faster twist with no bullet problems. Saw a 22-250 with 14" twist that 1 out of 3 or 4 would fly apart before reaching 100 yards. This gun was pristine and well oiled on the outside and owner said he kept it zipped up in a case. Upon closer inspection it was difficult to push a patch through bore. It was rusted severely. I have shot speer tnt's at 4100fps with extremely thin jackets. Made for explosive impact on lower velocity cartridges. Never had one come apart in flight, but that is through a hand lapped quality barrel with no rust or pits. It would be interesting to look with borescope in the bore of cousins 30-06. Even some new factory barrels are rough and do damage to the bullet.
He was also shooting through a thin stand of tall grass right in front of the deer. Running them fast with Superformance. Factory rifle - not sure of brand or twist. From my broader experience though, it seems the Hornady stuff (SST, ELD's) is a tad more susceptible than the Berger's. This is not an absolute statement. Just personal observation. No axe to grind, or snake oil to sell here. Have used ELD-M's with great success myself in 6.5 PRC and 7-LRM, though they do open up pretty explosively on target. (Not all bad) I've never ran one through a shoulder though. All clean "in the crease" hits.
