How does a DU round obtain accuracy?

generally cased in a sabot or with a coating.

It took me a minute. . . Depleted Uranium!

As a note, uranium wasn't chosen for its internal ballistics, but for its density and fracture properties. It's heavier than lead, allowing for high sectional-density projectiles. It's also quite hard, and tends to progressively fracture to a point when impacting armor.

Tungsten shares a lot of this advantage, but it's more expensive if you already have a pile of depleted uranium to get rid of.

db_tanker said:

generally cased in a sabot or with a coating.

Click to expand...

This is the correct answer.

DU is pyrophoric; it instantly heats the impact area, enhancing penetration. When a DU round hits an armored target there's a fire ball.

All you ever wanted to know about DU penetrators:

https://www.orau.org/PTP/collection/consumer products/dupenetrator.htm

I had “Ducks Unlimited” on the mind until I read the iranium post...

Ducks unlimited makes accuracy rounds?

Like little baby nukes

From Tactical ARs, to Strategic Thirty Aught Sixes.

Would the coating be lead? To shield from the radiation?

Demi-human said:

Would the coating be lead? To shield from the radiation?

Click to expand...

No.

Depleted Uranium is actually slightly less radioactive than naturally occurring Uranium.

Naturally occurring Uranium composition is approximately:

U-238: 99.28% (Half life: approx. 4.5 billion years)
U-235: 0.72% (Half life: approx. 0.7 billion years)
U-234: 0.0057% (Half life: approx. 250,000 years)

For a basic review, "half life" is the amount of time it takes for 1/2 of a radioactive substance to decay away. This means the longer the half life, the less radioactive it is. A 4.5 billion year half life, while not indicative of a "stable" isotope, is pretty darn close for relative comparison purposes.

U-235, with a half life of about 700 million years, is therefore more radioactive than U-238.

Depleted Uranium used by the DoD is about 0.3% or less U-235. With about half, or less, U-235 than naturally occurring Uranium, DU is therefore less radioactive than naturally occurring Uranium.

Also...

U-235 and U-238 decay by Alpha emission, the least penetrating of the ionizing radiation forms.

What this means is their decay process releases an Alpha particle, which is nothing more than a Helium nucleus (2 protons and 2 neutrons). This is a highly charged (+2), large mass emission particle.

This decay process is very important in understanding the relative penetration characteristics of a given form of radiation emission. For the purpose of this discussion, those types of radiation are:

Alpha (a Helium nucleus: 2He4)
Beta (an electron: e-)
Neutron (a neutron: 0n1)
Gamma (a photon with no electric charge or mass)

The most penetrating radiations are gamma and neutron. Gamma, because it is a high energy penetrating photon with no mass; Neutron because it is a penetrating particle with no charge.

The least penetrating are Alpha, because it is a large, highly charged particle; Beta because it is a low mass, charged particle.

It is extremely easy to shield Alpha and Beta radiation. Your clothing and dead layers of skin will stop these forms of radiation.

Neutrons, with no electrical charge, require a lot of shielding with substances high in hydrogen, like water or poly (a form of plastic).

Gammas, with no mass, require a lot of shielding with high density materials, such as the classic example of Lead.

Of interest, Alphas are CAPABLE of causing far more biological damage than gamma radiation...but the fact that they are incapable of penetrating even the dead layer of skin on the body means they have no capacity to actually do so UNLESS you breathe or ingest it.


The danger of Alpha radiation, therefore, is not in its penetration abilities, but in internal contamination. In other words, it has no ability to penetrate even the dead layers of skin on your body, therefore it cannot reach your internal organs. However, if you ingest or breathe it, then it may now expose your internal organs, such as lungs or GI tract, to ionizing radiation damage.


So the coatings are primarily for ballistic performance characteristics and maybe to assist in minimizing the possibility of spread of contamination (which would be minimal for solid metal anyway), not for shielding.


OK, the geeky nuclear engineer lesson is over!

Any questions?

Riomouse911 said:

iranium

Click to expand...

Two examples of DU projectiles:

1) 30 mm for the A-10 Big Gun. The bullet is not DU, but a penetrator inside it. This diagram is not great, as there's a copper (?) driving band as well, which is the only part that contacts the barrel, but it's not labeled here, nor is the steel windshield (outside of the bullet that provides the ogive).




2) 120 mm APFSDS (Armor-Piercing, Fin-Stabilized, Discarding Sabot), for the Abrams, as seen shedding the sabot here:


The dart with fins in the middle is the penetrator. Again, note the multiple colors. The DU bit is the rod in the middle, the tailfins are aluminum, and there's a windshield (nose cap) of some sort. Not sure what that's made of but I'd guess steel or tungsten.


The sabot is aluminum, and is the part that touches the barrel, but not the rifling, as... this gun is smoothbore, no rifling.


Short answer: A lot like how the M855 Green Tip can be fired through an M4 without destroying it. The bullet is not steel, but has a steel core you cannot even see.

entropy said:

Click to expand...

I was on the cell at the Orlando airport, didn’t see the typo. That’s a good one

Because--as noted above quite succinctly--the penetrator is sub caliber, its velocity tends to be much higher than a full-caliber projectile of the same weight.

If memory serves the US 120mm APFSDST round has a base diameter of 120mm but a projectile diameter of a mere 77mm. It has a muzzle velocity (IIRC) of over 4000 fps. Which is a number easy to gloss over.
Unless one considers it this way: That is 4/5 of a mile per second. If you will pardon my imprecision, it's in the neighborhood of a kilometer a second.

The 30mm round for the GAU-8 is a similar proposition (as are the 20mm DU rounds).

A very practical aspect of that is that you are reducing the need to lead targets. Which makes for better "end effect" on those targets.

black tip 9mm? heard that IMI made black tip 9mm for their Uzi carbines but beyond that...not sure? black tip on US ammo is for AP.
no mfg or .gov ever made sabot 9mm DU rounds though that I have ever heard of.

I had some of the black tipped IMI UZI 9mm years ago. It was good stuff, and loaded hot if I remember correctly.

shoobe01 said:

Two examples of DU projectiles:

1) 30 mm for the A-10 Big Gun. The bullet is not DU, but a penetrator inside it. This diagram is not great, as there's a copper (?) driving band as well, which is the only part that contacts the barrel, but it's not labeled here, nor is the steel windshield (outside of the bullet that provides the ogive).
View attachment 795611



2) 120 mm APFSDS (Armor-Piercing, Fin-Stabilized, Discarding Sabot), for the Abrams, as seen shedding the sabot here:
View attachment 795612

The dart with fins in the middle is the penetrator. Again, note the multiple colors. The DU bit is the rod in the middle, the tailfins are aluminum, and there's a windshield (nose cap) of some sort. Not sure what that's made of but I'd guess steel or tungsten.
View attachment 795613

The sabot is aluminum, and is the part that touches the barrel, but not the rifling, as... this gun is smoothbore, no rifling.


Short answer: A lot like how the M855 Green Tip can be fired through an M4 without destroying it. The bullet is not steel, but has a steel core you cannot even see.

Click to expand...

A better cross-section of the 30mm DU round used in the A-10 GAU-8 cannon:



In the case of the 30mm round the body of the round does touch the barrel but only the top surface of the lands. The driving/rotating band(s) is (depending on the particular round) a polymer, brass, copper, or soft iron band that forms to the rifling much as a bullet does in small arms making the gas seal and imparting the spin from the rifling. Driving bands are nearly universal in medium and larger caliber rifled weapons.

The aluminum body with a heavy metal core concept goes clear back to WWII. Both sides used rounds of similar construction although the heavy metal core was unusually tungsten-carbide since depleted uranium was not really a thing yet. The ballistics where not as well understood and many of these composite projectiles were notorious for having poor accuracy and also expensive to produce and thus only made and used in limited quantities during WWII.

Some larger calibers use bourrelet that are land diameter allowing the rest of the body of the round to be sub-caliber (except the driving band) to reduce barrel friction. Example below:

Black tip IMI 9mm (only) is supposedly a hotter SMG-specific loading. Some other rumors of carbine/SMG ammo are disproven or sketchy, so... not 100% sure if true.

The US made some DU rifle ammunition back in the 60s or so, down to at least 308. I have no idea why.

DU is very un-radioactive and not poisonous. But only when sitting there inside a shell. When you shoot it at armor, the end result is not unlike any other high speed projectile: a lot of it turns to dust and vapor. Ingesting DU is very not good thing and so I suggest you avoid battlefields where it's been used, but certainly do not eat and drink around the dead armor, and avoid being in an APC the US is shooting at of course.

Mostly, toxicity effects, vs radiological issues. Detailed here:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2819790/

CapnMac said:

Because--as noted above quite succinctly--the penetrator is sub caliber, its velocity tends to be much higher than a full-caliber projectile of the same weight.

If memory serves the US 120mm APFSDST round has a base diameter of 120mm but a projectile diameter of a mere 77mm. It has a muzzle velocity (IIRC) of over 4000 fps. Which is a number easy to gloss over.
Unless one considers it this way: That is 4/5 of a mile per second. If you will pardon my imprecision, it's in the neighborhood of a kilometer a second.

The 30mm round for the GAU-8 is a similar proposition (as are the 20mm DU rounds).

A very practical aspect of that is that you are reducing the need to lead targets. Which makes for better "end effect" on those targets.

Click to expand...

Well over 4000 fps.

5200-5700 fps at the muzzle.

https://en.m.wikipedia.org/wiki/Rheinmetall_120_mm_gun

CANNONMAN said:

Hey thanks. So what's the largest and smallest of these?

Click to expand...

I think the largest DU ammunition might have been the practice rounds for the Davy Crockett weapon.



This was a 155mm recoilless rifle that fired a projectile with an atomic warhead. The practice rounds needed to be the same weight, so they replaced the enriched uranium warhead with one containing depleted uranium.

mdauben said:

I think the largest DU ammunition might have been the practice rounds for the Davy Crockett weapon.

View attachment 795799

This was a 155mm recoilless rifle that fired a projectile with an atomic warhead. The practice rounds needed to be the same weight, so they replaced the enriched uranium warhead with one containing depleted uranium.

Click to expand...

Isn't that a NDU round? Non-Depleted Uranium. Or maybe an EU round? Enriched Uranium.

105 recoiless with the super caliber warhead, later the war head was put into other artillery shells of various size. The problem with Davey Crokett was what could go wrong with a Lt. and a jeep with a live nuclear weapon ?

mcb said:

Isn't that a NDU round? Non-Depleted Uranium. Or maybe an EU round? Enriched Uranium.

Click to expand...

No, the non-explosive, practice rounds contained DU.

mdauben said:

No, the non-explosive, practice rounds contained DU.

Click to expand...

Opps I missed the "practice" part of your post.