Regular readers know that I generally focus on law and politics, but a recent conversation with a police officer convinced me to talk “gun tech” for a change—especially since it involves safety.

“Mark,” a law enforcement officer I’ve known for years, recently related an incident that actually happened quite some time ago. Details of the story that follows have been altered slightly.

Mark and his partner were at a “cop friendly” diner for lunch. Given their shift assignment, “lunch” was around midnight. Like most cops, one of them was keeping an eye on the entrance.

About fifteen minutes into their meal, a man came bursting through the front door. He seemed clearly distressed as he ran right down the aisle, heading for the “Exit” sign at the back of the restaurant. Seconds later, another man came through the door…carrying a handgun.

Mark described the incident as “almost like a slow-motion movie.” Seeing uniformed cops, the startled intruder raised his gun, pointing it directly at the two officers. Mark was already bringing his own sidearm to bear. He fired one shot, dropping the armed man almost immediately.

Seeing the suspect fall, Mark’s partner held his fire. Both cops approached the fallen suspect, keeping their guns trained on him until it was determined that the suspect was indeed incapacitated (in this case, meaning dead).

In the weeks that followed, Mark received “high fives” from fellow officers. One shot, center mass, threat eliminated. “Good shooting, brother.” All’s well that ends well. Right?

It was then that Mark filled me in on “the rest of the story” (as radio icon Paul Harvey used to say). It turns out that the reason he had fired only one shot was not because he hadn’t tried; he had. But after the first shot, his gun had jammed!

Being a good cop, during the debriefing and inquiry that followed, he advised the investigating officers of what actually occurred, including that he had “topped off” his firearm’s 15-round magazine (i.e. after chambering a round, loaded one more round to bring the magazine back to a full 15).

What’s more, Mark related to me that the same thing had happened to another officer less than a year earlier. Once again, the problem appeared to be “topping off” the magazine after chambering a round. Interestingly, her sidearm was from a different manufacturer (she was from a department with different duty pistols).

There has been some study of this rare, but potentially catastrophic, malfunction. Most single-stack magazines do not exhibit similar difficulties; the heavier springs in modern double-stack magazines seem to be the culprit. Apparently, the increased pressure on the breech-block, combined with stress, adrenaline, and other factors, creates a combination of circumstances that can turn your “15 + 1” pistol into a single-shot weapon.

Personally, I never “top off” high-capacity, double-stack magazines. To me, reliability always beats one (hopefully) extra round. Even SEALS and other special operations personnel load only 28 rounds in a 30-round carbine mag.

How you handle this situation is your call. But my advice is to perform a simple test. After loading your magazine to capacity, try to push the last round down slightly. If you can depress the round about a ¼ of an inch, you’re probably OK topping off. If the fit is so tight that the top round barely moves, take the safe route and just “load, chamber, and go.”

Be safe.