He used a 1974 vintage 6mm Remington 700 BDL with a 3.5-10x Leupold and handloaded ammo with a 95 grain Nosler Ballistic Tip at 3117 fps via Ramshot Hunter.
I used my 10 - 15 year old 30-06 Remington 700 CDL with a 6x scope and handloaded 180 grain Berger Elite Hunter bullets at 2730 fps via Ramshot Hunter.
My son got his deer first after a terrific stalk to close the distance. He shot it at about 130 yards or so. Once, a killing shot, but it looked like the buck might go over the edge of a steep ridge, so he shot it again, dropping it right there.

He's been shooting that rifle nearly 20 years and took his first deer with it, as well as several other whitetail and mule deer over the years.
I stalked a bigger buck for three days, but he was always too far for me to be confident about the shot. Finally on the 3rd day, he had a nice looking 3x3 buck with him, and the smaller buck gave me a shot opportunity at 350 yards.

It had been a while since my son and I each got mule deer, hunting together. Felt real good. And the steaks have been wonderful.
Regards, Guy