SMG ammo description

[Winter]

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

I was trying to emphasize that it's the bullet we're talking about, not the whole cartridge. The cross-section there is of a complete cartridge -- bullet at the front (with steel penetrator and aluminium core), then the casing with the powder. The bullet is the only thing that goes out the muzzle. So the aluminium is not the 'middle bit', it's the rear part of the bullet. That makes it the core of the bullet, especially since that aluminium makes up about 70% of the bullet's total mass. The penetrator sits on top of the core, but is still part of the bullet as a whole, so your phrasing ""steel penetrator on an aluminium projectile", rather than an aluminium "core"" is wrong in firearms terminology.

Also, projectile and bullet do not always mean the same thing. A projectile can be anything fired from a gun, including but not limited to bullets. Even rockets and grenades can be projectiles under the right circumstances.

Regards,
Winter

[inquisiteur2]

a good projectile example would be the old energa for AK47.

[breversa]

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.

The soviet 5.45x39mm has a built-in air bubble in the tip (and they don't hide it), but its purpose is not to mushroom on impact like hollowpoint bullets, but to make it tumble, creating the same effect while technically not being an "expansive" ammo, thus still legal.

[Damp Squib]

The soviet 5.45x39mm has a built-in air bubble in the tip (and they don't hide it), but its purpose is not to mushroom on impact like hollowpoint bullets, but to make it tumble, creating the same effect while technically not being an "expansive" ammo, thus still legal.

Wheras (for what it's worth) much American ammunition is deliberatly weakened in the middle by crimping a deep groove where the cartridge case meets the bullet. This is ostensibly to waterproof the case, but has the "side-effect" of causing the bullet to snap in half when it hits flesh at a high velocity (meaning at a short range). The two bullet halves mushroom and veer off in different directions and the wound is filled with little bits of shrapnel.

This might technically be considered illegal, but nobody has ever put it to the test in an actual trial. People who capture American soldiers don't really tend to care about such nicities.

M4 carbines have a short barrel producing a lower muzzle velocity, so this effect happens only at a very short range. This has made the adoption of the M4 carbine as a replacement for the M16 rifle somewhat controversial as they are generally a less lethal weapon.

--
DS

[Damp Squib]

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.

The FAMAS rifle has the old standard of rifling grooves that turn once in 12 inches (and have only three grooves). What ammunition were you shooting? The newer NATO standard ammunition requires at least a twist of 1 in 9 inches, preferably 1 in 7.

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 ?

Well, yes, since aluminium has a lower density than lead. If the calibre is constant at 0.224 inches and the mass is constant at 31 grains than changing the density of the filler must change the length of the bullet (and push the centre of mass away from the tip).

Changing the length of the bullet both make the bullet less stable (causing it to yaw more quickly) and increases the rate at which energy is dumped when the bullet yaws.

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...

...and they have a flatter trajectory than 9mm SMGs and large capacity magazines to spray bullets from.

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

I have not located an official FN source connecting
a) the use of aluminium with
b) the often-quoted gelatin tests which show remarkable tumbling.
You should find such gelatin tests following the sources at the bottom of the wikipedia article on 5.7mm ammunition. Whether this yawing really occurs in practice is a matter of much debate.
a) and b) above are the two most remarkable aspects of the ammunition and since the laws of physics connect them so strongly I can't honestly think of a single other reason to use aluminium.

...

I'm curious to know why if the UFOAI SMG is 5.7mm, the pistol and machine pistols aren't also 5.7mm? 7.62mm is an odd calibre... it is the old standard Russian pistol calibre, using the same cartridge dimensions as the Mauser pistol from 1896. It's quite an antique compared with the 5.7mm.

--
DS

[breversa]

The FAMAS rifle has the old standard of rifling grooves that turn once in 12 inches (and have only three grooves). What ammunition were you shooting? The newer NATO standard ammunition requires at least a twist of 1 in 9 inches, preferably 1 in 7.

Wow, you seem to be well documented !
Yes, the F1 version in use within the french armed forces (except the navy which uses the NATO-standard G2 export version) still uses the old 12" turn.
We shoot "special" 5.56mm rounds made for a 1:12 twist for real use, and since rather recently standard NATO 5.56mm, manufactured by IMI (for the moment at least) and named "F5" model for training purpose. Those F5 rounds of course give lower accuracy, but also more fouling... and we all hate cleaning tar-like goo out of our rifles...

Well, yes, since aluminium has a lower density than lead. If the calibre is constant at 0.224 inches and the mass is constant at 31 grains than changing the density of the filler must change the length of the bullet (and push the centre of mass away from the tip).

Changing the length of the bullet both make the bullet less stable (causing it to yaw more quickly) and increases the rate at which energy is dumped when the bullet yaws.

That is ASSUMING the weight (and diameter) remain the same. While OTOH, I think that using a lighter core (= rear) without changing the length would shift the center of mass to the front, making the round more stable in flight. What do you think ?

...and they have a flatter trajectory than 9mm SMGs and large capacity magazines to spray bullets from.

It's a matter of propellant power/bullet mass ratio. The 5.7mm being bottlenecked, lighter and having more propellant shoots of course flatter than a heavier round with less load.

I have not located an official FN source connecting
a) the use of aluminium with
b) the often-quoted gelatin tests which show remarkable tumbling.
You should find such gelatin tests following the sources at the bottom of the wikipedia article on 5.7mm ammunition. Whether this yawing really occurs in practice is a matter of much debate.
a) and b) above are the two most remarkable aspects of the ammunition and since the laws of physics connect them so strongly I can't honestly think of a single other reason to use aluminium.

Well I can : stability.

I'm curious to know why if the UFOAI SMG is 5.7mm, the pistol and machine pistols aren't also 5.7mm? 7.62mm is an odd calibre... it is the old standard Russian pistol calibre, using the same cartridge dimensions as the Mauser pistol from 1896. It's quite an antique compared with the 5.7mm.

My guess is that the writer did not know that much about ammo and just heard taht the TT round has a good penetrating power for a handgun. I believe this argument is backed-up by the fact that the pistol description states it uses SINGLE-stacked magazine and at the same time boasting 12 rounds... A single-stack handgun would probably not hold that many rounds (too cumbersome), and if it were staggered-stack (as it should be in 2084 for not-too-wide rounds), its autonomy would be much higher.

[Winter]

I'm curious to know why if the UFOAI SMG is 5.7mm, the pistol and machine pistols aren't also 5.7mm? 7.62mm is an odd calibre... it is the old standard Russian pistol calibre, using the same cartridge dimensions as the Mauser pistol from 1896. It's quite an antique compared with the 5.7mm.

My guess is that the writer did not know that much about ammo and just heard taht the TT round has a good penetrating power for a handgun. I believe this argument is backed-up by the fact that the pistol description states it uses SINGLE-stacked magazine and at the same time boasting 12 rounds... A single-stack handgun would probably not hold that many rounds (too cumbersome), and if it were staggered-stack (as it should be in 2084 for not-too-wide rounds), its autonomy would be much higher.

I make mistakes sometimes, but that doesn't mean I'm ignorant.

My main reason for using varied calibres in UFO:AI's firearms is as a convenient and logical reason for our code-inability to share rounds between different magazine types. For example, you would not be able to use or exchange a pistol magazine for an SMG magazine even if we wrote them both as 5.7mm. You also couldn't load it into a different weapon because the number of rounds in a magazine is determined in script files by the weapon, not by the magazine. That means a 15-round pistol mag would suddenly turn into 50 rounds if we allowed it to be loaded into an SMG in-game.

And in my experience, firearm rounds tend to be fractionary rather than standardised. Look at how many there have been over the years. New ones are still being developed, whereas the only major standardised calibres have been the NATO (7.62x56 & 5.56) and Russian (7.62x39 & 5.45) rounds. With 8 major power blocks in the UFO:AI world, each with their own armed forces and an often-strained peace, I don't think the non-standardisation is implausible.

Regards,
Winter

[breversa]

Hey Winter, nobody's said you were ignorant : the firearms world is so big that few can claim to know everything about them... and that's why we're so happy to discuss the matter here and help you improve the game.

And about ammo, I was thinking of the following concept :

Instead of having ammo counted as "X rounds magazines for Y weapon(s)", why not consider having a "pool" of different ammo in the base inventory, and for each weapon using said ammo you'd have a button allowing you to tap into this pool and "create" a magazine out of it ?

Since I'm not feeling I'm very clear, here's an example :
You have a pool of 1000 rounds of pistol/SMG ammo in your base inventory. Next to it, you have two buttons : the fist one takes 12 rounds from the pool and creates a pistol magzine, while the second one takes 30 rounds out and makes an SMG clip.
Those magazines would stick to the cursor (as if you took them from the current inventory) so taht you can place them in the inventory. And if you clicked in the base inventory, they'd disappear and incremented the ammo pool again.

Do you see what I mean ? What do you think of that idea ? Probably not worth the trouble implementing, but who knows ?

[Winter]

And about ammo, I was thinking of the following concept :

Instead of having ammo counted as "X rounds magazines for Y weapon(s)", why not consider having a "pool" of different ammo in the base inventory, and for each weapon using said ammo you'd have a button allowing you to tap into this pool and "create" a magazine out of it ?

Since I'm not feeling I'm very clear, here's an example :
You have a pool of 1000 rounds of pistol/SMG ammo in your base inventory. Next to it, you have two buttons : the fist one takes 12 rounds from the pool and creates a pistol magzine, while the second one takes 30 rounds out and makes an SMG clip.
Those magazines would stick to the cursor (as if you took them from the current inventory) so taht you can place them in the inventory. And if you clicked in the base inventory, they'd disappear and incremented the ammo pool again.

Do you see what I mean ? What do you think of that idea ? Probably not worth the trouble implementing, but who knows ?

That idea has already been discussed among the devs in the past, but we have no coders with the free time and will to implement it, because it'd have to be part of a complete overhaul of the inventory system. So I write for the system we have, not the system we wish we had.

Regards,
Winter

[breversa]

Roger that.