Smith and Wesson 10-10 on the range with reloads

I'm reloading lead cast 38 special and the book said 3.6 grains should yield 900fps. I loaded 3.5. As you can see, the book isn't even close. That's why you test your experiments. There are many variables in this, so testing is imperative. However, when you find what works, everything is butter! #smithandwesson 10-10, #38special , #revolver