Tell me why not after please.

Potential to induce variance.. I always anneal then size. Bump the shoulder .0015” set a primer with a hand seater, drop powder and seat the bullet. I also don’t clean the cases until about shot #5

You anneal to return the malleability of the brass to new. In turn sizing is more consistent. In turn that makes neck tension more consistent. Split necks go away whether brass is annealed before or after sizing.

TAB…you’re not concerned with neck tension variances due to build up?

No sir, I have mic’ed many times and you truly can’t measure the carbon, it also acts as lube in the neck the bullet seating has a better feel than one that is clean brass.

Before… as SB and TAB mentioned.

I have broke down and started dry tumbling. It doesn’t clean carbon out of the inside of the neck unless it’s already loose. I never run a dirty piece of brass in a sizing die…carbon and other stuff can and will scratch your die.

Annealing after sizing can make each case neck have different rebound. Meaning, some might relax more than others.

Clean, anneal, size, trim, load in that order.

The reason why you anneal is to keep the brass malleable. If you reload and fire a case several times, at some point the case necks will become brittle or work hardened. And if you size a work hardened case, the case neck will crack during sizing. The purpose of annealing is to bring the brass back to "brass" (metallurgically speaking) and make it malleable again. If you size first, you can crack the necks. And the brass will not be as consistent.

Pretty well covered here, Gary. I'd just say that annealing makes the sizing operation work better in the first place, giving more consistent bullet pull. You can often tell when seating the bullet in annealed brass that the so-called neck tension is more consistent. Sizing first and then annealing really doesn't make much sense.