I won't offer proof but my 'smith's experiences. He has witnessed not one but two Sako mod failures at shooting competitions. In both cases the blown off extractor traveled up the lug raceway and right into the arms of the shooters resulting in serious injury. Both shooters carry that steel in their bodies to this day.
Needless to say he is not a fan and neither am I (of Sako extractor mods).
As for the 721s, I knew of two old timers who each owned one in 300H&H and they used them for a lifetime of hunting. Both rifles held up well.
MtnHtr
