Whitetail deer in Central Texas average around 90 lbs. for an adult doe, and the largest bucks average 150 lbs. Depending on the location, most are taken (shot) at ranges no greater than 100-150 yards. I've killed them with rifles ranging from 5.56mm to .308 Winchester (7.62mm), and with a .357 Magnum revolver (Model 686-3). My favorite deer rifle is a Savage 99c chambered in .308 Winchester. My recommendation for a good, all purpose medium caliber rifle is the .308 Winchester. Lots of different bullet weights available. Ammo is easy to find and affordable, and with the right bullet design and weight, and proper shot placement, you can take any animal on the North American continent.

I have a 6.8 SPC-II rifle I hope to use on deer and hogs this year as the MSR (AR platform) is more ergonomic and a bit easier to handle in the tree stand.

I also think the .300 Weatherby is overkill for whitetail deer. If it's all you have, then that's one thing. If you have the ability to get him in a smaller caliber rifle like the .243 Winchester or the 6.5, I think he would be better off. Now if he was hunting for larger game like moose, or elk, the .300 would be a better choice.

Good luck, I bet your grandson thinks you're the coolest Grandfather on the planet.

Regards,

Dave