3. CASE GAUGES: Acquiring case gauges for the calibers you reload is the best way to check that case length, headspace and case circumference dimensions are within specifications. Cases can be checked before and after loading to determine if your reloads will work in a semi-automatic chamber. It’s a pretty good bet that after the fourth reloading, your cases will be out of spec.
4. CHECK OAL: Overall length, or OAL, is the measurement of the loaded round. The SAAMI specification for the 5.56mm NATO cartridge is 2.260 inches, which allows it to fit and feed from a USGI AR-15 magazine. As an added measure, seat bullets to a maximum of 2.250 inches for more reliable function, and this OAL also corresponds to what I find ideal when shooting bullets like the heavier Sierra MatchKings and Berger VLDs.
5. HEADSPACE ISSUES: Headspace is the distance from the bolt face to the part of the chamber that stops the forward motion of the cartridge case. In AR-platform rifles, that is typically the shoulder. Excessive headspace occurs when a loaded round’s shoulder sits too far back from the chamber shoulder. Upon firing, the case stretches and may separate from the case head. This malfunction will lead to a stuck case in the chamber and probably a trip to your local gunsmith. Too little headspace will keep an AR’s bolt from completely engaging the barrel lugs, which can also lead to problems. A bolt not completely in battery when a cartridge fires can cause lugs to shear off or crack bolt heads. Insufficient headspace, at some point, will prevent the rifle from firing at all.
Sized or loaded cases can be checked with a case gauge. If the case is too long, then you need to screw the die down into the press until the case comes within spec. If your press arm is lowered and the die is touching the shell holder, the shell holder may require metal removal from its face to allow the case to be forced higher in the die to set the shoulder back. If you have a progressive press and a multi-stage shell plate, then material must be ground from the bottom of the die to remedy the situation. Cases that are too short require a more simplified fix. Just screw the sizing die out of the press until you solve the problem.
6. LOSE THE FAT: If your sized cases are too fat to fit into the chamber of your AR, you can’t put them on a diet. You can, instead, acquire a set of small base dies to squeeze the case body back to working dimensions.
7. DEPTH DUMMY: Depending on your bullet’s profile, the depth to which it is set in the case may cause it to engage the barrel’s rifling lands. If the bullet pre-engages the lands, it may cause problems. The projectile may be pulled from the case if a loaded round is extracted, dumping powder into the receiver and leaving a bullet in the bore. A bullet wedged tight in the lands may also spike pressures when fired, potentially causing damage to the rifle. The easiest and safest way to check bullet seating depth is to make a “dummy” round and check its function in the chamber. Inspect the bullet visually to find telltale signs of rifling land marks on the bullet. Also, measure the OAL of the dummy round before and after chambering.
8. HIGH PRIMERS: Visual inspection of loaded rounds is one way to check for high primers, which can cause malfunctions in your rifle. A round with a high primer may “slam-fire” when the bolt springs forward, or fail to fire at all. Another method to check for high primers is check during final loaded round inspection with a case gauge. You can get the hang of feeling for high primers pretty quickly.
9. TRIMMING THE EXCESS: When fired cases go through the firing and sizing process three to five times, there’s a pretty good chance that the case length is excessive. That’s when a case trimmer comes into play. A number of case trimmers exist, and I’ve used an old hand-cranked RCBS for years. I got tired of numb hands and arms after a session on the old-style trimmer, so I upgraded to a Hornady Loc-N-Load Power Case Prep Center. It’s much faster and doesn’t work me to death any more.