Here’s something informational for Sunday, Nicholas Moran explaining exactly how a modern 120mm (AKA 120×570mm NATO, the type used by the M1A2 Abrams and the German Leopard 2) APFSDS round works.
He has a dummy blue round to demonstrate the features. “All the projectiles are color coded. Explosive, for example, would be green with yellow lettering.” APFSDS rounds are black.
“The aft cap is the one piece which is left behind after a modern round is fired, and this takes up a lot less room than a traditional shell casing rattling around inside the tank once you fire it.”
A long primer rod runs up the middle for more even propellent burning.
“A modern tank does have a firing pin. It’s electrically fired, but it has a firing pin. It looks just like a firing pin you’d expect from a rifle, except it’s about yay long…Electricity goes through the firing pin, sets off the primer, which sets off the propellant, which gives you
the big boom.”
There are even emergency hand crank firing systems with dynamos to use if the electrical system goes down.
“The rest of the shell casing is made of a form of cellulose, and it is burned up in the explosion. So the aft cap is sufficient to seal the breach instead of requiring the entire casing to expand as you you’d find on a traditional round.”
“The catch is that this is simply not as robust as a metal shell.” Which is why the loader has to inspect rounds for scratches or bulges to the water-resistant coating. That could cause the round to break apart or misfire. “This is a bad thing.”
Which is why tank crews practice misfire drills to ensure safe handling of rounds so they don’t spread loose propellant all over the tank’s interior.
“The kinetic energy penetrator is itself a dart… it’s got fins at the back to keep the pointy end forwards, and it is kept centered as it goes down the tube by these sabot petals.”
“Modern sabots seem to have settled on three of these petals per projectile. Once the projectile has left the muzzle, the air is caught by the petals and they are peeled away.”
The discarded petals are a danger. “This is why sabot rounds such as APFSDS or M-PT should not be fired over the heads of friendly infantry.”
“The dart goes that way, hits metal, and basically punches through, taking little bits of metal inside with them. This is called a spall. These little fragments metal are extremely unhealthy to anyone or anything inside the vehicle which it hits.”
“However, if the armor is too thin to produce spalling, you get what is known as over-penetration. So you make a dart-sized hole on one side of the vehicle, a dart-sized hole on the far side of the vehicle, and dart sized holes on anything in-between, and outside of brown pants for the crewmen, quite possibly nothing else.”
“If so you’re firing such a target, you’re probably better off using a shaped charge round such as HEAT.”
He then show off a dummy HEAT projector, which has a funky blunt circular head that “in effect clears the air as a wind shield for the decidedly non-aerodynamic flat bit. The main body of the round also performs something of a stabilizing function and thirdly provides adequate standoff or room for the penetrating jet to form.”
“Here is a metal cone surrounded by explosives. The explosives detonate, the cone collapses the liner.”
Text popped up on screen at 9 minutes in notes that the penetrating jet is not high temperature plasma.
Here’s another video that provides a visualized simulation of how APFSDS rounds work.
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There are pics online of what the turret basket and interior looks like when the combustible case of Abrams ammo busts open unexpectedly. Definitely a poop-your-pants moment. 120mm propellant is a perforated extrusion cut into pellets about the size of a tater tot and stacked longitudinally inside the casing. There are thousands in there, and exposed they burn progressivley and with a lot of heat just like smokeless powder when heat is applied.
The combustible case is just as fragile as he describes. I’ve heard it is weak enough for one guy to break open by hand if slammed against your knee with both hands.
APFSDS would probably be overkill for many WW2 tanks. At least for the early ones. For a Tiger or Iosef Stalin, maybe Panther & T-34 it would be perfect.
Propellant fires ain’t no joke. One of the more thought-provoking moments of my very early military career was being within a few hundred meters of one of those early-1980s “moments of brilliance” that were so common back then.
Artillery units never use all the propellant that gets issued with each round. This leaves a bunch of excess propellant, which in those days was supposed to be carefully ignited and allowed to burn in piles of set safe size. The artillery outfit that was training near our bivouac site apparently was manned with a bunch of folks who didn’t read that part of the manual, and instead of having multiple separate smaller propellant fires, they decided to save the time and have one big one. Propellant is very energetic, and burns very, very hot. Small propellant fires like the ones they usually burn will literally melt the paint off of vehicles parked too close to them… When you stack an entire battalion exercise’s worth of propellant up in one big, glorious pyre, ignite it, and then stand back to watch from waaaaaaay too close? Yeah. Can you say “Melted the skin off several soldiers like the scene in Raiders of the Lost Ark”? I knew you could…
That was one ugly, ugly situation to have to come up on. There were a couple of the idiots involved who were basically incinerated, among who was the genius NCO that came up with the whole time-saving idea. I think there were at least three of the big 5-ton trucks they used for hauling ammo around that got reduced to frames and rims, as well.
That damn fire was bright, too. As in, you thought you were in daylight some 500m away bright…
[…] into Cuba, US army into woke BattleSwarm: Abbott Carries Through With Threat, Vetoes Slew Of Bills, How A 120mm Tank Round Works, and The Mine-Laying Lawnmower of Death Behind The Black: Looking down a canyon on Mars, Red China […]
Ah, Kirk, you know how it is with the good idea fairy. At least the NCO paid for his stupidity. A shame about the other guys.
Having been Navy, I’d never seen propellant burn. A friend who had been an 11B, posted a video on his blog showing mortar propellant being burned. Having seen that I would not want to see the propellant from tank shells burner. At least not anywhere close. Say, they same county.
When I played tanker in the TARNG, all our main gun ammo was cased. Those were M60 days.
There are pics online of what the turret basket and interior looks like when the combustible case of Abrams ammo busts open unexpectedly. Definitely a poop-your-pants moment. 120mm propellant is a perforated extrusion cut into pellets about the size of a tater tot and stacked longitudinally inside the casing. There are thousands in there, and exposed they burn progressivley and with a lot of heat just like smokeless powder when heat is applied.
The combustible case is just as fragile as he describes. I’ve heard it is weak enough for one guy to break open by hand if slammed against your knee with both hands.
APFSDS would probably be overkill for many WW2 tanks. At least for the early ones. For a Tiger or Iosef Stalin, maybe Panther & T-34 it would be perfect.
Propellant fires ain’t no joke. One of the more thought-provoking moments of my very early military career was being within a few hundred meters of one of those early-1980s “moments of brilliance” that were so common back then.
Artillery units never use all the propellant that gets issued with each round. This leaves a bunch of excess propellant, which in those days was supposed to be carefully ignited and allowed to burn in piles of set safe size. The artillery outfit that was training near our bivouac site apparently was manned with a bunch of folks who didn’t read that part of the manual, and instead of having multiple separate smaller propellant fires, they decided to save the time and have one big one. Propellant is very energetic, and burns very, very hot. Small propellant fires like the ones they usually burn will literally melt the paint off of vehicles parked too close to them… When you stack an entire battalion exercise’s worth of propellant up in one big, glorious pyre, ignite it, and then stand back to watch from waaaaaaay too close? Yeah. Can you say “Melted the skin off several soldiers like the scene in Raiders of the Lost Ark”? I knew you could…
That was one ugly, ugly situation to have to come up on. There were a couple of the idiots involved who were basically incinerated, among who was the genius NCO that came up with the whole time-saving idea. I think there were at least three of the big 5-ton trucks they used for hauling ammo around that got reduced to frames and rims, as well.
That damn fire was bright, too. As in, you thought you were in daylight some 500m away bright…
[…] into Cuba, US army into woke BattleSwarm: Abbott Carries Through With Threat, Vetoes Slew Of Bills, How A 120mm Tank Round Works, and The Mine-Laying Lawnmower of Death Behind The Black: Looking down a canyon on Mars, Red China […]
Ah, Kirk, you know how it is with the good idea fairy. At least the NCO paid for his stupidity. A shame about the other guys.
Having been Navy, I’d never seen propellant burn. A friend who had been an 11B, posted a video on his blog showing mortar propellant being burned. Having seen that I would not want to see the propellant from tank shells burner. At least not anywhere close. Say, they same county.
When I played tanker in the TARNG, all our main gun ammo was cased. Those were M60 days.