SMG ammo description

[Stalins Organ]

sometimes I can be Mr Picky....

It fires an upgraded version of the Belgian 5.7mm armour-piercing round, a steel penetrator with aluminium core....

Um.....it's got to be some really amazing technology to have an aluminium core for AP ammo - one would normally expect AP ammo to have a hard core such as steel, tungsten or DU, and the aluminium to be the outer material to reduce weight thus increasing velocity and AP performance.

[Winter]

sometimes I can be Mr Picky....

It fires an upgraded version of the Belgian 5.7mm armour-piercing round, a steel penetrator with aluminium core....

Um.....it's got to be some really amazing technology to have an aluminium core for AP ammo - one would normally expect AP ammo to have a hard core such as steel, tungsten or DU, and the aluminium to be the outer material to reduce weight thus increasing velocity and AP performance.

It's based off of the current-day 5.7x28mm cartridge, which is a steel penetrator with an aluminium core.

Quoting from Wikipedia:
"The SS190 AP ball FMJ is designated as Armor Piercing (AP) ammunition, designed to penetrate body armor. Its sale to civilians is restricted. The SS190 bullet has a steel penetrator and an aluminum core."

We do our research before we write things down.

Regards,
Winter

[Alex]

I bet the steel adds weight to the projectile to give it enough momentum to pierce the armour, while having a softer core allows it to deform as it penetrates the armour, so when it reaches the flesh it breaks apart and makes a mess of a persons insides.

[breversa]

Deformation usually goes against penetration, so I'm also puzzled as to why an aluminum core instead of a steel one. Is there any metal specialist here who could tell us the compared caracteristics of steel and aluminum (hardness, density, etc) ?

[Alex]

Yeh, where's a metalurgist when we need one?

From WikiPedia:http://en.wikipedia.org/wiki/Armor-piercing_bomb

The entire projectile is not normally made of the same material as the penetrator because the physical characteristics that make a good penetrator (tough, hard metal) make the material equally harmful to the barrel of the gun firing the round.

[Voller]

I would say the picture on wikipedia says it all: aluminium on the outside, then comes the hard steel shell to do the penetrating, then comes the charge and fuse.
The softer material on the outside is to make sure that the barrel of the gun firing it doesn't get damaged in the process.

[Stalins Organ]

Quoting from Wikipedia:
"The SS190 AP ball FMJ is designated as Armor Piercing (AP) ammunition, designed to penetrate body armor. Its sale to civilians is restricted. The SS190 bullet has a steel penetrator and an aluminum core."

We do our research before we write things down.

Good to hear.

Looks like it was just a difference in interpretation - seperated by a common language.

A cross section of the SS190:



As you can see the steel bit is the tip, backed by an aluminium body.  this gives the ligtest possible projectile (high velocity) with a hard tip (superior penetration).

To me that would be described as a "steel penetrator on an aluminium projectile", rather than an aluminium "core", which implies the middle is aluminium.

But at least you spell "aluminium" correctly!! :lol:

Cheers

[Damp Squib]

Deformation usually goes against penetration, so I'm also puzzled as to why an aluminum core instead of a steel one. Is there any metal specialist here who could tell us the compared caracteristics of steel and aluminum (hardness, density, etc) ?

Aluminium is used to make the bullet longer than if the traditional material, lead, had been used.

The intension is that the bullet destabilises in flesh tumbling sideways cutting a wide slot instead of poking a small hole. If the bullet had been shorter, the slot cut would be less wide, and less damaging.

--
DS

[Stalins Organ]

I don't know about the length issue, although it is certainly of prime importance in ballistics, but http://www.d3lf.net/p90/ammo.htm says that the role of the aluminium body behind the tip is to tumble after penetration, and that this is achieved by it's greater weight than the steel tip, which seems odd since the all-lead SS193 subsonic round is exactly the same length (it is also cross sectioned on that page).

I suspect the effect occurs because the 2 parts are not joined, other than being enclosed in the jacket, but tha't just supposition and I don't know any details on how it would happen.

Anyway - the net effect is that hte SS190 is supposed to ensure that there is no "over-penetration" - ie no-one behind the target gets hit with rounds that have already hit the target, or bystanders behind flimsy protection such as soft building walls do not get seriously injured by strays.  All the while still assuring excellent penetration......so 2 contradictory requirements to be met - good penetration, but not too much!

[Winter]

As you can see the steel bit is the tip, backed by an aluminium body.  this gives the ligtest possible projectile (high velocity) with a hard tip (superior penetration).

To me that would be described as a "steel penetrator on an aluminium projectile", rather than an aluminium "core", which implies the middle is aluminium.

No, I don't think you're interpreting it quite rightly. It's the bullet that has a steel penetrator and an aluminium core, which -- as you can see in the cross-section -- it does.

I may have worded it a bit poorly in the article, though. Will have a look at it.

Regards,
Winter

[breversa]

I guess it's the word "core" that misled me into thinking it was the INNER part of the bullet, instead of the REAR part.

But still... Why aluminium and not lead for the rear part ? Are ammo designers concerned about lead toxicity in the target's body ? :-P

But I think I know the reason why : it's a matter of density.
A bullet with steel tip and lead core would be too homogenous and may be prone to yaw in flight, while a bullet with steel tip and aluminium core would have its weight shifted to the front, causing the core to "follow" the tip in its flight, acting like a stabilizer.

Lowering the global weight of the bullet will also make it less prone to over-penetrate, as required.

I guess we're done with that mystery aren't we ?

[Damp Squib]

But I think I know the reason why : it's a matter of density.
A bullet with steel tip and lead core would be too homogenous and may be prone to yaw in flight, while a bullet with steel tip and aluminium core would have its weight shifted to the front, causing the core to "follow" the tip in its flight, acting like a stabilizer.

Bullets don't yaw in flight, because they are spun by rifling. Long bullets are less stable than short bullets and require a steeper rifling twist, but this is otherwise not an issue when the bullet is in the air.

Long bullets, like the bullets in question, destabilise when they leave the air and enter flesh. This is desirable, the bullet cuts a wider, nasty wound when sideways than when point-on. The military are prohibited from using hollow-point bullets that would similarly make larger wounds (prohibited from use on people, aliens not so much).

Using a long aluminium bullet instead of a short lead bullet is entirely to make it less stable (and cut a broader wound when it spins around). Using a long aluminium bullet instead of a long lead bullet is to make it lighter and faster, with more energy (the subsonic 5.7mm rounds carry perhaps one-quarter of the kinetic energy of the supersonic rounds).

--
DS

[breversa]

Bullets don't yaw in flight, because they are spun by rifling. Long bullets are less stable than short bullets and require a steeper rifling twist, but this is otherwise not an issue when the bullet is in the air.

Yes, they DO yaw (moreless, depending on many factors). I've experimented it enough times when checking my targets after FAMAS rifle shooting : some bullets even impact SIDEWAYS.

Long bullets, like the bullets in question, destabilise when they leave the air and enter flesh. This is desirable, the bullet cuts a wider, nasty wound when sideways than when point-on. The military are prohibited from using hollow-point bullets that would similarly make larger wounds (prohibited from use on people, aliens not so much).

While it's true that military conventions ban the use of hollowpoint bullets, and that yawing increases the wound channel of a projectile, I doubt that's the reason of the aluminium core. But until we get some facts about it,, we may leave that matter aside for now.

Using a long aluminium bullet instead of a short lead bullet is entirely to make it less stable (and cut a broader wound when it spins around). Using a long aluminium bullet instead of a long lead bullet is to make it lighter and faster, with more energy (the subsonic 5.7mm rounds carry perhaps one-quarter of the kinetic energy of the supersonic rounds).

Are those aluminium-core bullets really longer than lead-core ones ?
But indeed, a lighter bullet can go faster, and since E = 1/2mv² (v = speed), impact with more energy than a heavier but slower one. However, light bullets are more affected by wind and are less precise, and still, one aim of the P90 is to be able to defeat body armor at ranges up to 200m...

DS, do you have any source to your arguments ? I found that debate interesting and would like to know the truth about it.

[Alex]

The military are prohibited from using hollow-point bullets that would similarly make larger wounds (prohibited from use on people, aliens not so much).

An aquantance of mine from the army told me that a "Manufacturing Defect" (in inverted commas with a wink and a nudge) leaves a small air bubble near the tip of the bullet, which effectively makes it a hollow point upon impact.

so much for rules of engagement.

[Stalins Organ]

As you can see the steel bit is the tip, backed by an aluminium body.  this gives the ligtest possible projectile (high velocity) with a hard tip (superior penetration).

To me that would be described as a "steel penetrator on an aluminium projectile", rather than an aluminium "core", which implies the middle is aluminium.

No, I don't think you're interpreting it quite rightly. It's the bullet that has a steel penetrator and an aluminium core, which -- as you can see in the cross-section -- it does.

I don't understand what the difference is you're highlighting bullet for sorry - I said projectile, which is the same thing.

Breversa wrote:

Are those aluminium-core bullets really longer than lead-core ones ?

No they are not - see the web page I linked to - the homogenous bullet is exactly the same size as the aluminium/steel one.