I guess I’ve become a gun guy, although I didn’t set out to be one. Over the years, I’ve acquired ownership of eight handguns — a total that seems to qualify me for the designation. Then again, I’ve spent my entire adult life in law enforcement. I suppose that if I’d devoted those years to, say, carpentry, I’d now own an impressive collection of hammers.

Initial reports from the scene of our latest bloodbath in Aurora, Colo., indicated that the gunman was armed with two Glock pistols, a Remington 870 shotgun and a “Smith & Wesson AR-15.” Gun people like me immediately realized this information had to be inaccurate because “AR-15” is a registered trademark of Colt; the S&W version of the rifle is called an MP-15.

The misnomer was similar to describing the getaway car used in a bank robbery as a Ford Impala — it could have been one or the other, but it couldn’t possibly be both as an Impala is made by Chevrolet.

I don’t mean to trivialize an atrocity by delving into the minutia of nomenclature. After all, the reporter got the big story dead right: lunatic armed with very potent weapons shoots lots of innocent people. But the fact that the mistake survived editorial vetting illustrates an obstacle to reasonable discourse about our national gun problem — namely, that many well-intentioned people often don’t understand what they’re talking about.

Before proceeding to the most recent atrocity in Colorado, allow me to define some basic terms.

A weapon’s caliber is determined by the diameter of the bullet it fires. The knockdown power of a round is a function of the size of its bullet and the speed at which it travels. Magnum loads, for instance, contain extra gun powder to propel faster-moving bullets.

Revolver handguns and manual-action rifles hold fewer rounds than their semi-automatic counterparts. This lower capacity means that the shooter has to reload more often, which is generally not a problem for the sportsman but can be a decided disadvantage in combat.

They also can’t be shot as rapidly: With a revolver, the cylinder has to rotate between shots and with the manual rifle, the shooter has to manipulate a bolt or lever between shots to clear the spent round from the firing chamber and reload it with a fresh one.

Semi-automatic firearms, on the other hand, self reload. Every time it is fired, the gun automatically ejects the spent round and reloads the firing chamber. These weapons are equipped with spring-loaded magazines that hold the live ammunition. The bigger the magazine, the higher its capacity — larger magazines provide for more shooting between reloads but the shooter still has to pull the trigger for each shot fired.

Fully automatic weapons are machine guns. Hold the trigger down and the thing will fire until the magazine runs out of ammunition. Thankfully, machine guns are still federally regulated and thus not generally available.

The 1994 assault weapon ban that Bill Clinton managed to ram through Congress sought to outlaw so-called “assault rifles.” These were high capacity, semi-automatic rifles originally designed for military use. Though these weapons are capable of rapid fire, they don’t shoot nearly as fast as a machine gun.

An AR-15, for instance, is a semi-automatic weapon. The fully automatic version of the same rifle is called an M-16. The M-16 can fire 800 rounds a minute, while the AR-15 can “only” discharge about 60 rounds in the same time period.

Certain provisions of the ban were silly but others made a lot of sense. Some weapons were banned because they looked sinister. Military-style stocks were frowned upon, although they do not affect the rifle’s operation. Bayonet mounts were outlawed even though bayonet charges are not a major urban problem. These were primarily aesthetic judgments that had little bearing on the weapon’s actual lethality.

But other aspects of the law addressed relevant concerns. One of these was the ban on high-capacity magazines for semi-automatic weapons. The 10-round limit placed on these devices was a reasonable compromise between a marksman’s legitimate use and prevention of wholesale slaughter.

Unfortunately to get the bill passed, sponsors had to agree to include a 10-year sunset provision in it. By the time the original law expired, the NRA had purchased large segments of the Congress and it was allowed to lapse.

The psychotic clown in Colorado was thus able to purchase a 100-round magazine for his assault rifle — along with 6,000 rounds of ammunition — to prepare for an evening at the movies. These purchases were made from the comfort of his home via the wonders of the internet.

As a gun guy, I’m sympathetic to concerns about self-defense. We presently average about 16,000 murders a year in the United States. That works out to about 44 killings a day. And as the saying goes, when seconds count the cops will be there in minutes. Who can blame a citizen for taking measures to protect himself?

But I leave the reader with a quandary to contemplate: At what point does self-defense become self-destructive?