Star Member The Polack MSgt (1,882 posts)
31. Sorry to be "that guy" but - no
Caliber is the diameter of the projectile, gauge refers to how many standard loads make a pound -
12 gauge = 1.25 ounces of shot, 16 gauge = 1 ounce of shot, etc..
A .410 shotgun is a 28 gauge, and the projectile is .41 inches in diameter
Well, you're warmer, but still wrong. It's not how many ounces of shot go in a standard load, it's how many round balls in that size could be cast from a pound of lead. 12 gauge = 12 balls per pound. Although practically unheard of now, single round ball loads were once the standard equivalent to modern slugs.
The .410 is just out of the whole normal gauge system, it's a cailber-system measure, along with .44 shotshells and some other oddities measured in mm that are now just historical curiosities. There were gauge-system rounds, like 32 gauge, in similar bore sizes, it's just an accident of history that it was the .410 that became the sole survivor rather than the .44, 11mm, or 32 gauge.
And no, the .410 is no beater of a real pistol round in the same projo range, it operates at a considerably lower pressure than a real pistol round, a .410 slug is kind of in the range of a .38 S&W (Not the .38 S&W Special, but the older stubby round)