Unit of fire

The unit of fire is an old military concept, a rough prediction based on prior experience, that says how much ammunition is likely to be fired from a particular weapon in one day of combat: the rounds per day needed for each weapon. At the link, see the U.S. Army's estimate from the WWII era.

A rifleman was expected to let loose 150 rounds a day. The BAR gunner's unit of fire was 750 rounds a day. These estimates were revised downward for the Marianas campaign in the Pacific, 100 for the rifle, 500 for the BAR.

What I found interesting about this is riflemen in WWII used less ammo than I had thought. Something else that caught my eye was that the unit of fire for the 12 gauge shotgun was only 25 shells per day. Reasoning this through, I suppose it makes sense if we assume that the fellow with the shotgun only fired at close targets, since buckshot is no good against distant targets, and he frequently hit what he was shooting at. Buckshot is tops for hit probability at modest range.

Perhaps these numbers will bring relief and comfort to the fellows who feel they are chronically short of ammo and are distressed by the current shortage. Target games such as trap shooting make us think that 25 shotshells are not a lot, and some rifle guys use up a hundred rounds, or more, in one or two range sessions. But in case of some sort of hypothetical disaster scenario accompanied by an armed emergency, that's actually a lot of ammo. That is to say nothing of hunting. Some deer hunters feel they are wasting money if a box of 20 rifle cartridges does not last several years. Two or three shots to confirm the zero before the season starts, one or two shots for the deer and they're done until next year.

So if you feel you are short on Zombie Apocalypse ammo, perhaps you're not at all as hard up as you think.