Summing up the good advice you have received above......A really good powder measure isn't cheap but is a must. Also, all of them must have a baffle installed. Some powders measure better than others. Your operating technique must be as exactly the same every time as much as you can master. Then the point I want to make......a slight variation in powder weight from cartridge to cartridge has about the least affect on accuracy of all the myriad of variables in putting a batch of reloads together. Caution must be observed when using very fast burning powders in small cases. Also, when loading rifle cartridges to the very max. The best accuracy for any loading is always obtained some where below maximum load. There are always exceptions to every generalization. You need to read everything you can about reloading. Some of the published books and articles should be read multiple times.

One last bon mot: Reloading is a situation where the Law of Diminishing Returns comes into play quite often and quickly.

A second bon mot I just remembered: Every firearm is different in small ways from any other. The individual firearm is a law unto itself when accuracy is the goal.