.30 cal airgun whitetail head?

I know someone who's grandpa lived through very tough times. Starvation was a real possibility for his whole family. I'm not speaking on the ethics of this but I know for a fact that he used a 22lr and only did headshots on deer. I believe if a 22lr will kill one a 30 cal going 911 should have no issues. I like these kinds of questions BTW and think they are fun to think about. I won't be doing head shots this deer season because imo it's not ethical. They can turn their head at the last second and you can miss. Definitely not ideal. However if you are poaching in the middle of the night to feed your starving family. Perhaps a good moderated 30 cal would be a fine choice. I remember a few years back on a YouTube video a dude killed a deer with a factory 25cal marauder. I found it distasteful and wrong and said so but again I am not going to jump on anyone's case for broaching the subject. 
 
Last year Texas approved hunting deer with airguns ,30cal and 215 fpe minimum, I took 3 dear last year with my Benjamin bulldog shooting cast 148gr slugs all head shots all DRT , I hunt small acreage where if they run to a neighbors property it would cause problems ,a heart lung shot deer can run 100yrds easily, thats why I use a head shot just below and forward of the ear is lights out . But you need to keep the shots 50yds and under. By the way no pass through on any of the deer sbot last year YMMV.