I’m tempted to say it serves you right for reading other shooting magazines but I shall stay my hand and try to answer your question sensibly.
‘Overkill’ means causing a great deal of collateral damage when, for example, an airstrike is called in to wipe out a village because there is a sniper in the church tower.
When it comes to deer stalking and shooting an individual animal, dead is dead and that’s the end of it.
If you suspect that the .308 might smash a lot of meat, let me set your mind at rest.
Some years ago I was lent a Lakelander rifle (one of the best production rifles I have ever handled) in .308 and we shot everything with it from Red to Muntjac.
I well remember BASC’s then Head of Education shooting a Muntjac end-on (from in front, of course), and finding the bullet in the haunch as he was carving the family dinner.
There was absolutely no meat damage.
The bullet was a nice, round nose 180 grain and it had done no harm to the deer’s flesh at all.
Apart from sudden death, of course.
I leave you to draw your own conclusions and wonder, perhaps, whether the use of a smaller, higher velocity round such as the .243 would have produced such a happy result.