There is an elephant in the room which you forgot...
So consider shooting an elephant with a 416 Rigby. 400gr ME=5115ftlbs.
Elephant weighs 3 tons (2240x3=6720lbs)
5115/6720=0.7611ftlbs/lb.
I have shot loads of roe & red with a 243 hit them correctly in the right area and they will go down, heart & lung shots seem to run a short distance,
I hit a 9 kg roe kid last week with my 308/150 grain broke its front shoulders and he still ran 50 yards with not much blood trail found him with the dog, goes to show that you need a dog close by at all times.
I'm chopping my .243 in for an FAC air rifle following a video I saw![]()
90gr Nosler Partition, 40gr H380 = mv 3045ft/sec 1860ft/lb give or take - imo you shoot to your ability/equipment capabilities, if I am out stalking with the .243 then anything under 150yds is as dead as a dead thing provided I do my bit, however if a Roe/Munty/Fox presents a shot at 150+yds then it would be taken, should any of the larger species turn up it would be a close the gap or not take the shot situation, if I expect shots to be taken at the further out distances ie hill or open land then it would be .308 time launching 168grains of good news.
If you shoot enough then you will get runners, then forget muzzle velocities/ bullet calibre its the 22kg of GWP that sorts things out....![]()

oh god..... 243 rant time. The .243 is not anything more than a foxing calibre that's good for roe. Comparably a 17hmr shooting roe deer is more powerful than a 243 shooting a red stag, here's you maths and no I'm not saying it is legal or acceptable to shoot a deer with 17hmr:
17hmr v's 40lb roe deer (assume for the story it's a 'hunting' style bullet not v-max)
Bullet energy at muzzle 240 ft/lb
Deer live body weight 40lb
Energy delivery = 6ft/lb per live weight pound
243 v's 300lb red deer (assume the bullet actually meets legal energy in England for the large deer1,700ft/lb)
Bullet Energy at muzzle 1,700ft/lb
Deer live body weight 300lb
Energy delivery = 5.7ft/lb per live weight pound
Er hello, your .243 kung foo is not strong..... it is weak like baby mouse!
If you don't believe me about the energy to live weight correlation then consider the reaction of the example deer shot with the energy discussed assuming a 'good' chest shot. Both deer will jump and run before collapsing shortly after, but hit them badly and you're looking at a wounded and suffering deer if a lethal follow up is not made.

i dropped a 105kg in the jacket red stag at 135 yards with my .243, it took a couple of strides and was stone dead. When we opened it up the heart was smashed to bits by the 100grn round - good enough for me!
Exactly, reasonable distance, decent bullet = a very dead thing!
oh god..... 243 rant time. The .243 is not anything more than a foxing calibre that's good for roe. Comparably a 17hmr shooting roe deer is more powerful than a 243 shooting a red stag, here's you maths and no I'm not saying it is legal or acceptable to shoot a deer with 17hmr:
17hmr v's 40lb roe deer (assume for the story it's a 'hunting' style bullet not v-max)
Bullet energy at muzzle 240 ft/lb
Deer live body weight 40lb
Energy delivery = 6ft/lb per live weight pound
243 v's 300lb red deer (assume the bullet actually meets legal energy in England for the large deer1,700ft/lb)
Bullet Energy at muzzle 1,700ft/lb
Deer live body weight 300lb
Energy delivery = 5.7ft/lb per live weight pound
Er hello, your .243 kung foo is not strong..... it is weak like baby mouse!
If you don't believe me about the energy to live weight correlation then consider the reaction of the example deer shot with the energy discussed assuming a 'good' chest shot. Both deer will jump and run before collapsing shortly after, but hit them badly and you're looking at a wounded and suffering deer if a lethal follow up is not made.