i stated a shotgun with the right combination can kill deer in their tracks at 70 yards.

NOT every shotgun is capable of pattering buckshot. I own 2 of these and I use them to bird hunt with ONLY.

old timer elaborate a little bit on your qualifying.
gun used, barrel restriction (whether fixed barrel or choke tube) buckshot used. and what was the qualifying goals?

ally
4b is effective out to the distance that your gun will put 80% load in vitals of animal you are hunting.

I use 4b out to 30 yards or close shots with dense cover. 3in rem has 41 pellets and my goal is to put min of 30 in kill zone. otherwise I use 30 cal pellets in 1b and 00b.

I spend almost 3x as much time shooting my shotgun at paper vs. shooting my rifle at paper.

if you are unsure about a 40 yard shot then you should spend few hours looking down the bead of your shotgun at paper getting you a better combination of gun/choke/ammo.

again it is up to the shooter/hunter to do the right thing.
1 get right combination
2 only take shots you are 110% confident in.