Rimmed and belted cartridges are properly positioned in the chamber by the rim thickness or the distance from the base of the case to the top of the belt, respectively. Rimless and rebated cartridges have either bottlenecked or straight/tapered cases. The former have a reference datum on the shoulder that positions the round in the chamber, while the latter typically headspace on the case mouth.

When a cartridge is discharged, the case must expand to seal the chamber so the combustion products push the bullet out of the barrel and hot gas doesn't leak back through the action and into the shooter's face. If the sizer die is not adjusted to ensure proper headspace, the cartridge may not chamber at all (too long), it may misfire (too short), or the case may not seal the chamber properly.

The manufacturers' instructions clearly describe how to properly set the sizer dies to assure the handloads fit the firearm's chamber to perform these critical functions reliably and safely. Rimmed or belted, bottlenecked cases should be resized by adjusting the sizer die just like you do with a rimless, bottlenecked case. By doing so, you will optimize cartridge-to-chamber fit and avoid excessively stretching the case body. Both conditions help ensure the case will seal the chamber and will not fail prematurely.

While I'm on the subject of resizing, you will have to experiment with various products and techniques to learn how to properly lubricate the cases. I've resized thousands and, until recently, never stuck one in the sizer die. However, I had to use my stuck-case remover kit twice in the last six months. Both times I was in a hurry and failed to apply enough lube to keep the case from seizing in the die.

Sticking a case in the die can cause you to overreact to avoid another incident. However, applying too much lube can cause unsightly or even unsafe lube dents. If they're large, then the case shoulder has been weakened, and you should discard it. Small ones will safely iron out when the round is fired.

The last significant step required to ensure proper case preparation prior to reloading is verifying each case is not too long. Remember the importance of cartridge-to-chamber fit? A reamer that is machined to prescribed dimensional tolerances precisely cuts the chamber. This includes the throat portion and where it ends. Each time the case is fired and reloaded, it will stretch and grow. Hot loads and full-length resizing accelerate case growth.

If you chamber a round that's too long, the case mouth will be crimped into the bullet by a step at the end of the throat. When the round discharges, the case mouth can't open to release the bullet properly, and pressure can spike dangerously. The brass should be measured after every resizing and trimmed if the overall length exceeds the specification. Be sure to deburr the case mouth inside and out before seating a bullet.

For handgun and rifle handloads that require applying a crimp to hold the bullet securely, you should trim each batch of cases to a uniform length. If you don't, you can't consistently crimp the case mouths, and some will be loose while others that are too long may be damaged by the bulletseating/crimping operation.

Another case preparation step that needs some attention is prepping the primer pocket. I always uniform the pockets externally before loading the first time. Each time the fired case is resized, I clean the pocket and often do so with the same tool I used to uniform the pocket. I rarely deburr the flash holes internally unless I'm preparing a batch of benchrest ammo and am taking every precaution to achieve top accuracy. It takes a lot of time and significant effort to process a large batch of brass; however, you only have to do this once.

Practically speaking, case life is directly related to how well you take care of your brass. Sloppy loading practices and hot loads will cause premature case failure.