You could take a look in your manual and it will give you various loads for the calibers you mentioned. Read the chapters in the begining of the manual and read the sections in the book for the 45 LC and 44 Mag. It should give you some load data for different bullet weights and different powders. Pick a powder that will work for the bullet weight you want to shoot and see if it works for both calibers. Buy a pound of that to start. If you have several options, post them here and someone might have some suggestions. The other thing is if you pick a Hodgdon powder from the Speer book, you will have some data from the website above that might help you pick. Check out the Hodgdon website because it covers Winchester and IMR powders also. I try to buy versatile powders that will work for more than one caliber. That way I don't end up with a whole bunch of different powders. At least when you're starting out you probably won't be too worried about having the "perfect" powder for each caliber. Right now you really just want to get started and get some safe loads under your belt. The first few times I reloaded I ended up bulging some cases because I crimped them too much. That's when I bought my bullet puller. Those were .41 Mag pistol cartridges. Good luck, have fun and BE SAFE.