Another reasonable practice is to find two or three sources for data and average out their starting weights. Say you had one source at 3.5, another at 4.2 and a third at 4.7 grains for a starting charge. Average those out and you get 4.13, or round it down to 4.1 grains. That will likely result in good operation for your pistol, but you'll probably find that a higher charge weight is best for both cycling the action and good target accuracy.
Become as knowledgeable about reloading as you are your snakes and all will be well!
Thank you everyone for all the advise. I reloaded that range brass last night 4.7gr and shot it this afternoon. It went great!