Probably Just The Cold

Got a comment suggesting that M1 Carbine ammo in Korea wasn't up to snuff.

I can't find the information they're citing, but the looking for it did turn up some interesting stuff about cold weather and ammo performance.

An Army publication for snipers (FM 3-22.10, Sniper (Dec 17) referenced in this link) says the round will impact 1" lower at 100 yards per 20°F the temperature is below the temperature when you zeroed the gun.

FM 3-22.10 pg. 4-147. The change in the point of impact is best determined by referencing past firing recorded in the sniper data book. As a rule of thumb, a 20-degree increase in temperature will raise the point of impact by one minute; conversely, a 20-degree decrease will drop the point of impact by one minute. 

And that's with a spitzer shape, not a round nose; like the .30 Carbine!

Chosin was -35°F and if the troops had zeroed on a nice 75°F day there's a 100 degree difference, or a 5" change of impact at 100 yards.  10" at 200.  15" at 300...

That's assuming the cold soak didn't weaken the springs so bad the hammer doesn't hit hard enough to set off the, now, less sensitive primer...

Norma published a video showing that .30-06 lost velocity as it got colder.

Everything is in Godless Metric.

Room temperature average velocity is 2,625 fps.

28°F ammo is 2,575 fps. (1.9% drop)

0°F ammo is 2,532 fps. (3.5% drop)

Norma specifies 2,772 fps. for this round from a 24" barrel, so we're also seeing the effect of losing 2" of barrel in the test.

2,772 gets us the bog-standard 7d pi from .30-06.

2,625 drops it to 7d-1 pi.

2,575 gives 6d+2 pi.

2,532 gives 6d+2 pi. 

A 3.5% drop in velocity for an M1 Carbine goes from 1,990 fps. to 1,919.5 fps.

That drops it from 4d+1 pi to 4d pi.  Still plenty of energy to penetrate winter clothes.

Losing another 3.5% to get to Chosin temps (baseless extrapolation here) gives 1,850 fps and 4d pi.

With these numbers one cannot help but concur that the troops were missing their targets.

There's a couple of sources that mention the Chinese troops were drugged to the gills.  I've written about another case of bad shot placement and drugged up opponents before: Juramentado. 

Oh Most Didn't

In writing about the effects of .38 Long Colt on a juramentado, it should be noted that the berserker Moro that got to bolo range is the exception rather than the rule.

Most of them died well short of machete range well ventilated by .30-40 rounds from the infantry.

The scale of the firepower brought to bear was actually astounding by the standards of the day.

Civilize Them With A Krag

Starting at the same 10 yards as with the pistol, our corporal fires his M1896 at the charging juramentado.

As with the revolvers, shot placement matters.

Bad rolls will fuck you here.

Assuming we're aimed at the beginning of our turn at 10 yards, we fire at +2 to skill for a 14 to hit the torso and 11 to hit the vitals.

If they don't drop or you miss, 11 for the torso at 5 yards then 13 at contact.

Going for the vitals hit normally drops them dead right there with a single shot.

Getting two torso shots normally almost gets to the berserker stopping -5x HP.

Three torso hits occasionally fails to stop them right at your feet.

.38 Long Colt VS .45 Colt

While dropping the .38 Long Colt model of 1892 for the proven .45 Colt model of 1873 against the Moro and the juramentado made the men feel better.

It was likely that the slower rate of fire and reload time of the older gun forced the shooter to pay more attention to the fundamentals and get better shot placement.

FuzzyGeff and I ran several combinations of a juramentado charging an Army lieutenant with every issue handgun from the period and the M1911.

It came down to die rolls more often than not.

But one thing was certain, taking your time to get a vitals shot was far more effective than plugging the Moro in the torso.

The extra damage from the .45 Colt didn't come to bear as much against the berserk disad of the juramentado as you might think.

3x 2d-1 pi is more than 1x 2d+2 pi+ (18 vs 13) after all.  IF YOU ACTUALLY HIT! And panic firing double action the full RoF of 3 every turn leaves you with an empty gun and a Moro close enough to smell.

Update: If the juramentado gets into spear/bolo range the soldier loses.  We had to tweak the scenario several times to give the guy with a gun a better chance against the berserker.