I have no formal training with any kind of ballistics. I'm learning as I go. I know that too much powder is bad but so is too little powder. Too much powder can lead to over pressure conditions and possible kabooms. What happens with too little powder?
At the moment I'm playing with 45 ACP, Accurate No 5, and a new MP mold 45-225. With Lyman #2 my bullets are coming out at around 224 grains for the solid bullet (haven't played with any hollow points). I'm powder coating the bullets. In order for me to get the assembled cartridge to fit both my gun (HK 45) and my Cartridge gauge I have an OAL of 1.180".
Yesterday I loaded and shot several different loads ranging from 6.9 gr to 7.9 gr in 0.1 grain increments. Average velocities ranged from 796 to 891 fps. Charges below 7.3 grains have widely spaced velocity spreads and large Standard Deviations. Once I get to 7.3 gr charge, these numbers tighten right up and look (to me anyway) what I'd consider to be normal ranges.
Am I correct to assume that the lessor charges are what is giving me the velocity spreads and Standard Deviations that I'm seeing? Are those large spreads and deviations signs of too little powder (which I assume means not enough pressure). What are other signs to look for when it comes to lesser charges? (I'm not considering a stuck bullet in this grouping of symptoms.)