General > Discussion
SMG ammo description
Winter:
--- Quote from: "Stalins Organ" ---I don't understand what the difference is you're highlighting bullet for sorry - I said projectile, which is the same thing.
--- End quote ---
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:
--- Quote from: "Alex" ---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.
--- End quote ---
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:
--- Quote from: "breversa" ---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.
--- End quote ---
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:
--- Quote from: "breversa" ---
--- Quote from: "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.
--- End quote ---
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.
--- End quote ---
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.
--- Quote from: "breversa" ---
--- Quote from: "Damp Squib" ---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).
--- End quote ---
Are those aluminium-core bullets really longer than lead-core ones ?
--- End quote ---
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.
--- Quote from: "breversa" ---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...
--- End quote ---
...and they have a flatter trajectory than 9mm SMGs and large capacity magazines to spray bullets from.
--- Quote from: "breversa" ---DS, do you have any source to your arguments ? I found that debate interesting and would like to know the truth about it. :)
--- End quote ---
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
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