"He pulled the trigger on the reduced load, the gun doubled with excessive recoil"

Is it possible that part of the problem is that the gun doubled, perhaps caused by the shooter causing the doubling ie; finger slipped off the front trigger or both fingers in the trigger guard.
the reason I ask is no one has addressed this or mentioned it. I just don't see how a single cartridge would do that damage to a rifle like that, They are pretty stout build guns. But then I don't use fillers in anything and have never loaded for a cartridge over 45-70 size.
Would be interested in hearing what anyone has to say.