I spent a large part of my youth not far from chromo of off blanco basin road

ive killed them with my 270 win and 150gr partitions DRT.
killed one with a 50 cal round ball at 80 yds
ive killed a stray small bull here in texas that im assuming was really lost with 1 shot from a 22 mag in the neck.
ive even killed one with a arrow going 240fps.

they arent hard to kill, its where you hit them. only one ive ever lost was with a 340 weatherby. i aimed for a high shoulder shot at about 225 yds, and i either pulled the shot or he took a step, and hit him a little far back. dropped like a sack of taters, and i watched him not move for about 20 minutes. by the time i decided to go over too him, he was still down and not moving. had to go way around a steep drainage between me and him and when i got there that bull was gone! i mean vanished with just a little blood where he laid down at the shot. looked for 2.5 days and never found him or a drop of blood. only thing we came up with was i hit him in the void under his spine and above his lungs, the shock put him down and in the long walk over he recovered and shagged away.
anyone find a decent 5x6 in the valle vidal in 2002 its probably mine

You have a lot of good suggestions to consider. I started hunting elk in 1980 and did well with a 270, but in 1987 I give up rifle hunting and started hunting with a 50cal black powder rifle and had good luck with that until I turned 70 . Find you a gun that you feel comfortable with shooting from a rest or leaning on a tree are what ever.You want get many chances to shoot from a bench rest, and black powder season does not have the crowd of people that regular rifle season does. Good luck and be safe.

Curious what bullet you used and how far was the shot? Thanks

Have killed 4 bulls at 35, 175, 365 and 410 yards. All with 300 win mag with 180 grain nosler ballistic tip. Not one ever took a step.

Bigger bullets usually cause more damage all things else being equal. I would recommend getting a gun chambered in the largest cartridge that you can comfortably shoot well and then practicing quite a bit.

Smaller, lighter bullets can fragment and cause lots of hematoma, scattered lead throughout your animal.
Bonded heavier bullet do not fragment and hit hard without lots of ancillary damage to meat.

I think this is way over stated, But thats a different topic.

I've used 7mm-08 140 TTSX, 280 150 NBT, and 308 155 Scenar-L for elk, one mule deer and one scimitar oryx.

Your 30-06 will do well unless you need an excuse for another gun.

Yeah , you're probably right but I haven't had issues with heavier bullets doing more damage.
Bad shots do the most damage.

I'd hunt with whatever caliber I feel most comfortable with. Shot placement is more important. My 1968 Remington 308 dropped a Canadian moose. I'm sure smaller calibers would too. I have been enjoying my 300 win mag at the range, I'm sure it will work too.