Not to sound flippant,... but, the BEST resource is a minimum of four or five reloading books and crossed referenced to two or three online sources. It sounds like a lot of research, but, I think it pays off in the long run! Hell, how can anything be more important in reloading, than being confident in a powder charge choice!
On a side note,...I think the most valuable habit I have developed, when researching the most pertinent load data,... is, when I am all done and finished,... I go back and double check again!
I just did this yesterday. I came across a very old note/entry on a 300 BLKOUT load that just didn't seem right, before going further into researching/confirming the load. My note was a typo, I wrote Extreme powder when I meant A-1680,... catching myself, making mistakes, by double checking, is both scary and satisfying.
I have a couple Lyman books and a Lee, which are my first and my final check points before I check my scale with a "Lyman Shooter's Weight Check Set" before weighing,... https://ads.midwayusa.com/product/1012866166?pid=212586&utm_medium=shopping&utm_source=google&utm_campaign=Reloading+-+Metallic+Reloading+Equipment+(Not+Presses)&utm_content=212586&gclid=CjwKCAjwhOD0BRAQEiwAK7JHmAwdUICEFlx8TliiVP0kYOpkoV4FRvx9W6X-AgIOhWvjqiqJb53lghoCbxIQAvD_BwE ,... which I use every time I sit down at my bench to charge cases,... even if I get up for some reason, when I come back, I double check my scale!!!
IT IS BY FAR THE MOST IMPORTANT TOOL I HAVE AT MY BENCH, IMO!!!