I've been reloading for close to 15 years and go 100 percent by what the reloading manuals say. There is a lot I don't understand about burn rates, compressed loads, case capacity......etc, but by following the load data in the manuals, I have never had an issue. I came across something today that confused me. Any time I have loaded a particular caliber with a particular powder using two different sizes of bullets, the smaller bullet always called for more powder. For example, if I'm loading .45 colt with Unique powder using 200 grain and 250 grain bullets, the load data will show that more powder is used in the 200 grain load. Recently I loaded some 240 grain .454 casull using IMR 4227. The manual called for 33 grains of powder. I then loaded some 150 grain .308 using IMR 4227 and the manual called for 24 grains. I would think that the .308 being a larger case and smaller bullet, would call for more powder than the .454 casull. I'm just curious as to why this was the case. The load data is coming from the Hornady and Lee manuals. And don't get off on the, "why are you using IMR 4227 powder in these calibers when there is better powder out there." I have quite a bit of IMR 4227 and just wanted to see how it performed. Thanks.