The old warning, "Don't ever shoot ammo reloaded by anybody but yourself" has saved shooters a lot of grief over the years. Another should exist: "Be afraid of your own sloppy reloading habits."
Poor reloading habits seem to commonly fly under the safety radar. Most of the newer firearms available today are very strong, allowing small reloading mistakes to go undetected.
Below are several of the most common issues that make "reloading" synonymous with "hazardous." Avoid these, and you and your appendages are likely to survive to see many more years of shooting your favorite reloads.
Micro cracks around the neck, shoulder or base of the cartridge case often go unnoticed. At best, escaping gasses seep through the action — and sometimes into the face of the shooter — when cracked cases are fired. At worst, the case can rupture completely, leaving brass in the chamber. Cracked cases may also blow superheated gasses rearward or even propel case fragments through the action. Before reloading, turn each case in your fingers and examine it carefully, searching for cracks. Bright rings around the base of the case about 0.4 to 0.6 inches up from the rim can indicate potential case separation.
Cases Dented by Sizing Lube
Excessive application of sizing lube can cause divots in cases, particularly bottlenecked rifle cases. Most reloading dies are built with a tiny vent hole to assist excessive lube in escaping, but such holes have limited efficiency. When too much lube is applied, sizing is very easy, but excess lube builds up in the die/case shoulder area. Because lube has hydraulic properties and is not compressible, the buildups create dents in the malleable brass cases.
Firing dented cases swages the divots out, but in extreme examples, the divots can diminish case capacity, boosting pressures. Plus, the divots overwork the brass and can cause fatigue, which leads to cracking or splitting.
Excessive Powder Charge
This is the scary one that everybody talks about and avoids. Oddly enough, magnum rifle cases are usually at the least risk, since they use slow-burning propellants that just barely fill the available space. Handgun cartridges, on the other hand, are often easily double charged. When loading with a single-stage press, charge a complete case trays' worth of cartridge cases. Before seating bullets in them, use a flashlight to scan the tray for any cases with powder levels that appear high or low. If you're loading with a progressive press, spend the money for a powder level check system and install it.
The worst possible scenarios involve the use of incorrect powder types, for instance mistakenly using pistol or shotgun powder to charge rifle cases. The result is a forensically disassembled rifle and the potential for serious injury. Isolate powder types, and have only one canister on your loading bench during any given loading project.
Inadequate Primer Seating
Primers that are not quite fully seated can lock up actions. Plus, the protruding portion of the primer can be sensitive to impact, especially in semiautomatic firearms that ram fresh cartridges toward the chamber. It's important to keep primer pockets clean of fouling buildup and be sure to seat primers fully in their pockets. They should be seated just a few thousandths deeper than the plane of the case head. Using hand tools is the easiest way to accomplish this. Close attention to the priming systems on progressive presses is necessary to keep them functioning appropriately. Particularly, be sure that no loose powder particles or other debris finds its way to the top of the primer ram, denting primers and interfering with clean, straight seating.
Overzealous Primer Seating
Don't be too aggressive when seating primers. As discussed previously, it's important to have primers seated fully below the surface of the case head. Ramming them too firmly into the primer pocket can actually cause problems. The anvil (the three-footed portion inside the primer, designed to seat against the bottom of the pocket and provide the firing pin something against which to smash and detonate the impact-sensitive priming compound) can begin to crush the priming compound prematurely, causing ultra sensitivity in the primer. Develop a feel for seating primers firmly without crushing them.
Trimming cartridge cases is a lousy job. No matter how you skin that cat, it stinks. As a result, using untrimmed cases that are too long is one of the most common mistakes reloaders make.
Depending on your chamber dimensions, you may get away with it for a while with certain firearms. Bolt actions, with their superior camming strength, will usually chamber cases that are too long. But if the case neck becomes long enough that it begins to contact and crush against the end of the chamber, accuracy decreases. Semiautos, on the other hand, are easily crippled by cases of excessive length. I've seen AR actions locked up so hard by an out-of-spec cartridge that failed to go into battery that the shooter had to pound on the charging handle with a 2x4 to extract the stuck case. That's bad AR health care.
Unfortunately, semiauto rifles tend to cause more case stretch than any other type of firearm. Grit your teeth and trim those cases when they grow out of spec. It will save you from considerable pain in your hindquarters later.
Bullets Seated Too Far Out
Precision rifle shooters tend to like seating uber-accurate match projectiles too long, intentionally causing them to engrave into the rifling ahead of the chamber. Undoubtedly, many rifles shoot their best with match bullets seated thus, and the practice is arguably fine for use in precise shooting and competitive work. But beware of loading hunting projectiles to engrave on the rifling. Many long-range hunter types shoot soft, match-type bullets (a practice I disagree with) on big game, and they seat their handloaded bullets to engrave. When the hunter goes to remove a loaded cartridge from the chamber, there's significant risk that the bullet will stick in the rifling and the case will pull off of it, spilling powder in the chamber and all through the action. I personally witnessed as a good buddy lost a beautiful 5x6 bull elk because he'd done just that and couldn't chamber a fresh cartridge to shoot it with.
Bullets Shaved by Case Mouths
More often than not, when you seat rifle bullets into new, unfired cases — and often when seating in once-fired factory cases — the crisp 90-degree inner edge of the cartridge mouth will shave fine curls of copper from the bullet's jacket as it enters, potentially interfering with accuracy. Make a point of chamfering the inside of new rifle cartridge case mouths with a low-drag case chamfer tool such as Lyman's VLD chamfer reamer
Where necessary, a good crimp secures the bullet against movement. However, especially in handgun cases, reloaders sometimes apply too much of a good thing. The result? Bulges in the case mouth just below the crimp area, creating a cartridge that will most likely fail to chamber. This is particularly likely to happen when reloaders attempt to seat and crimp the bullet in one operation. It's far better to seat all the bullets first and then crimp as a final, separate action. And crimp just enough. There's no need to distort the case neck and squeeze the bullet out of shape.
On the other hand, if you don't crimp enough, certain cartridges can give you real trouble. Primarily, these are magnum revolver cartridges and straight-walled cartridges loaded for lever-action rifles.
Magnum revolvers recoil stoutly and can cause heavy, lightly crimped bullets to creep slightly forward with each shot. If they creep far enough, one will protrude out of the mouth of its chamber and come against the revolver's frame as the cylinder rotates, locking the gun up and putting you out of commission.
Cartridges loaded into the tubular magazine of a lever action rifle undergo significant pressure from the magazine spring, which compresses and exerts rearward pressure to feed cartridges into the action. The more cartridges stuffed into the chamber, the more the pressure increases. If bullets aren't crimped adequately, a bullet can pop right down into the cartridge case, leaving your rifle crippled because it can't feed a short, sharp-rimmed case out of the magazine and into the chamber.
The solution? Crimp your bullets just the right amount, of course. Sometimes, experimentation is necessary to figure out that magic quantity. As a side note, freshly trimmed cases crimp much more consistently than do mixed lot cases of varying length.