Like others I shoot other people's gun quite often if offered. I also allow other to shoot my 1911 or even s&w 500. I put my own reloads in my own gun when I shoot it. I never offer my reloaded ammo in the other people's guns.
Most people take me up on the offer to shoot my 1911. A little less than half decide to shoot the 500. I have some mouse loads, some medium loads, and a hot load for it. Most of the shooters only shoot the light and medium loads.
I only offer my guns to people that appear safe and generally familar with guns.
Sharing is part of the fun I have at the range.