My old tang safty M77 in 7 Mag has taught me more about reloading in the last 30 years than all the other rounds combined..... And I'm still confused at times
two things its really taught me is pay attention to the resizeing die! If I resize all the way to the shelholder on either of the two resizeing dies I have the case is toast in three round MAX. If I just bumb the shoulder back a very little or just neck size I can get 5+ reloadings with no problems.
The second thing its taught me is that H1000 and R22 sometimes works depending on the lot!!!!!!!!!! Had an old lot of R22 years ago that we where 7 grains over book on with no preasure signs and it shot great with this load. The next lot I got Blew primers a grain under book. The tell me the new lots of H1000 will do the same thing useing old info.
The other thing is its a lot fussy about ammo. It dont like accubonds or most polimar tips for that matter but prefers 160 Partisions and will shoot MOA out past 500 with numerous powders including H870,IMR7828,H4831sc,H4350,R22 & R25