Are those 240gr FMJ-FPs jacketed or plated?
Yes, in a revolver you need to crimp into a cannelure unless it is a powder puff load...and even then, you will need sufficient neck tension to hold the bullet under recoil. The bigger the bang, the firmer the crimp. In slow burning powders like H110/W296, one needs a consistent firm crimp to insure consistent burn for best accuracy.
Following published loads the use of H110/W296 is no more dangerous for a newbie reloader than any other powder. No powders should be used outside published recipes by new reloaders(or old reloaders for that matter). H110/W296 have narrow parameters, but perform very well when used within those parameters and are very safe. They are actually safer than many powders because they are virtually impossible to double charge because of the volume one uses. Anywhere between 23 and 24 gr under any 240 jacketed bullet and you are safe. IMR4227 and 2400 are also great powders if one wishes a little less velocity that H110/W296, with IMR4227 proving to be a little more accurate for me in my firearms. It also can be downloaded safely to mid level loads when one is tired of full power loads.