All those different steps to prevent a bad/double powder charge are good, however, the single most important step, a critical step, is to visually check every casing, just before seating the bullet. I also only load 50 rounds at a time. Back in the day, I use to weigh the powder for every round, which is IMHO, a huge waste of time! Any quality powder dispenser, once set, will continue to drop the same charge over & over.

The most important thing you can do, without question, is to visually inspect each casing with a flashlight. It takes less than a minute, to carefully inspect a 50 round block of loaded casing. If you have a double or even a missed charge, that's is where you'll spot it!