I inherited a Ruger #1V 22-250 and a Weatherby Varmint Master 22-250. I have the original owner's load data. I thought it would be good to know what the max bullet weight is?

The Varmintmaster won't shoot heavy bullets worth a darn. Do you want to sell it?

I was worried about that! No, I think I'll keep it.

I Imagine they are both 1 in 14 twists.

55 and short 60 grain bullets are probably the upper limit.
There are some heavier bullets that will stabilize due to their blunt shape. the 63 Sierra smp and 70 speer SP are two that will work. The 63 Sierra is super accurate and a killing machine, well worth a try

Enjoy your new rifles and try to keep shrapnel from beating you out of them.

Thanks for your input and advice.

Bullet length is probably more critical than weight. When I had my #1 22-250 it shot .805" long 64gr Winchester power points well enough. 60gr Partitions not worth a dam. Best accuracy was with 55gr flat base Sierra which are .715" long. The 70gr Speer semi pointed had usable accuracy and its length is .790". Pick bullet that is short and you will be fine. Anything over .800" is going to be problematic in a 1-14. Faster you push them the better they will be.