Correct me if I'm wrong, but aren't 12.7mm rounds and .50 inch rounds the exact same thing?
Soo... I'm firing the exact same bullets from my Anti-materiel rifle and my 12.7mm pistol? This seems a bit absurd.
Why have two different varieties of ammo that are the same caliber?

Also, "anti-materiel" is french, isn't it? So why does it use .50, which is a U.S. measurement, instead of 12.7mm, the SI equivalent?

Hm, you're right. 12.7mm does in fact equal half an inch... I don't know much about guns/bullets, but this seems pretty weird.

I think the equivalent rifle IRL can use .50 as well as the others ones but I might be wrong. I haven't seen 12.7mm rounds anywhere in the game yet. Are they just really rare?

Edit: Just checked the wiki and this is what it has to say "The Hauer Premium 12.7mm civic defense round is a consumer-grade pistol round of identical diameter to the military-grade .50 caliber, but less powerful. It is probably similar to the real-world .50 AE magnum pistol round. "

So apparently the 12.7 has less gunpowder than the .50 cal or something else like that.

Love to know how you fire a 12.7 from a Sub Machine gun too...

Just remember, its the Fallout Universe, they have laser guns too

Well of course. I stopped worrying about realism the first time I picked up a gun made out of a pipe and a tin can, and my character DIDN'T lose a hand upon firing it.

I've only ever gotten them off the bodies of dead Legion Assassin's. There was this one that ALWAYS spawned outside of 188 in my game, every day he'd be there, and always has 12.7mm rounds and a sub-machine gun to shoot them with, cept that one time he has a pistol.

the great khan carry 12.7 mm pistols and rounds.

Its not the same bullet. Lets take the .50 caliber bullet for example. The .50 caliber bullet fired from a Desert Eagle for example is much different than the one fired from a .50 caliber Machine Gun or Rifle. Same situation here.

I found my first 12.7 pistol AND smg in a cave... I believe it was a night-stalker one. Bloodborne cave, perhaps?

Ah, that makes sense. Thanks for clearing that up.

Well the .50 BMG and the .50AE are completly different, so I assume thats the case here.
You wouldn't be able to get your hand around the grip of the 12.7mm pistol if it used .50BMG.

Caliber refers to the diameter of the bullet. A bullet that is half an inch across is a .50 caliber round, or .5 of an inch.

Bullets of the same caliber don't always come in the same size. Your Anti-Materiel Rifle is a .50 rifle, just as your 12.7 mm pistol is a .50 handgun. BUT they use two different .50 rounds. The AM Rifle utilizes a .50 BMG (Browning Machine Gun) round, which is a very thick, very long rifle round, where as the 12.7mm pistol utilizes a .50 AE (Action Express) or equivalent .50 handgun round.

In short, same caliber, different sizes. Trying to put a .50 BMG into your 12.7mm pistol would be like trying to fit a bowling ball into a small shoe.

The .50 MG round in the game is referring to the .50 BMG round that the US military uses in weapons like the Barrett M82 Anti-Materiel Rifle or the Browning M2 heavy machinegun. The NATO designation is 12.7x99mm.

The 12.7mm round in the game likely refers to the Russian 12.7x108 round judging by the size and shape of the round displayed on the Pip-Boy. Then again, it could be an entirely different round that was developed in the Fallout universe only. Whatever the case may be, it's probably not the right shape to fit into the Anti-Materiel Rifle in Fallout: New Vegas so that would explain why you can't use the 12.7mm round in it.

Edit: After firing the 12.7 submachinegun and watching the ejected cartridges, I noticed that they appear to look like a .50 caliber pistol round instead of the rifle round displayed in the Pip-Boy. If this is the case, that would make firing the weapon much more managable and would mean that the rounds fired are more likely based on the .50 Action Express or .50 GI rounds irl.

materiel is french by origin, but means military ordinance in america also

I think the wiki described it as European in origin (not entirely sure) so its probably Russian.

Anti-materiel doesn't mean that it's a French weapon, it just means that the weapons are for taking out more solid objects, as opposed to anti-personnel; anti-materiel weapons in the US, such as the Tac-50 are "anti-materiel" and it uses .50 cal rounds. And yes, .50 cal. sniper rounds are essentially 12.7 x 99 mm NATO rounds. Perhaps the fact that the 12.7 mm ammo is used for pistols, and the .50 is used in a larger rifle warrants the fact that they are two separate ammos in this game.

I'm going to post a couple of pictures

http://upload.wikimedia.org/wikipedia/commons/thumb/8/82/CartridgeComparison.jpg/400px-CartridgeComparison.jpg

http://upload.wikimedia.org/wikipedia/commons/thumb/8/84/Rifle_cartridge_comparison_w_scale.png/300px-Rifle_cartridge_comparison_w_scale.png

Quite a large difference, eh?

Especially when you note that the far right in both pictures is .22 Long Rifle, making direct comparison across the two photos easier. And in the photo with the .50 BMG, starting from the right we have .22 LR (In-game, silenced .22 Pistol/.22 SMG) 5.56mm NATO (Any 5.56 weapon in-game...Varmint Rifle, That Gun, etc.), 7.62 x 39mm (NOT in-game), .308 Winchester (Hunting Rifle, Sniper Rifle), .300 Winchester Magnum (NOT in-game) and finally- The Beast, .50 BMG as used in the Anti-materiel rifle.

The pistol round pic also has 6 in game ammos. .50AE, .44 mag, .357 mag, .40 is almost certainly the 10mm, 9mm, and .22 LR.

10mm is a real-life cartridge.

they are the same diameter sure, but so are .30-30, .30-06, .308 and .30... and they're not mutually compatable.

Also "Materiel" is French yes, but in military parlance "Materiel" is a term used to refer to any military object, if it's not personnel it's materiel. An Anti-Materiel rifle is a modern term for a gun halfway between a WWII-era AT rifle and a modern battle rifle. They are used as long-range sniper rifles because the beefy .50 BMG round they fire has a range of over a mile, great for fighting in terrain where you have sight lines that long, like, say, a mountainous country like Afghanistan.

However the real purpose of an AMR is to engage light armor assets like armored cars (the military vehicle called an armored car not your local Brinks truck), IFVs and even helocopters.

Edit: oh and add 7.62mm to the list of rounds roughly the diameter of a .30-06.

Nice, way to come clutch with the excellent visuals. Above and beyond the call for helpfulness.

I have a friend who calls the .50AE a baby carrot and the .50 a carrot. She has food related names ammo, my favorite is the Tic Tac, known to normal people as a .22LR. She used to get so much crap at the range

I dont know if anyone else has pointed this out but we have the same thing in real life. 50 cal. desert eagle hand gun, and a 50 cal. snpier rifle, the bullets are not interchangeable due to casing size.

Wow, since i don't use the imperial system, i didn't know that. In the game though, they are both different.

Well, almost. .40 Smith & Wesson is to 10mm as .38 Special is to .357 Magnum, or .44 Special to .44 Magnum. "Same round, only shorter and weaker."

http://en.wikipedia.org/wiki/File:357Sig10mm40sw.jpg