I did buy the imr sr4756. I have berrys 124grain plated bullets. The data ive found list 125 fmj. So is there much difference between a 124 and 125 grain bullet and fmj and plated?
I was thinking the same thing. I figured id start lower than that and work up a little. Ive seen data for 147 lead nose starting at 3.5. So 4.9 for 124 plated seems weird.
Don't take this personally, but this post illustrates two point of reloading ignorance that need to be addressed.
Some powders are only suitable for a given cartridge/bullet combination with a narrow range of charge weights. Do not "figure" you know better and use a starting charge weight that is lower than the manual lists. The specified range was from 4.9 to 5.4 grains. If you cannot be that precise in charging your 9mm cases, you probably should not be reloading.
You mention seeing data for a heavier bullet that starts with less powder and that is "seems" weird to you. Heavier bullets are longer. Longer bullets have to be seated deeper into the case. This leaves less room in the case for powder. Hence, heavier bullets OFTEN have a lower charge weight than lighter bullets. There is nothing at all weird about that!
Until you have done a lot of reloading and really understand what is going on, do not second-guess published load data. Do not attempt to apply logic or reason to the process, just stick to the SCIENCE of reloading. If you have specific questions, ask someone or read up on it. There is very little grey area in reloading, so if you don't KNOW something, don't attempt to reach any conclusions about it. That's how guys get themselves in trouble.