demographic said:
.338? never heard of that one as I thought that the US military used to use .308 winchester and now use .223 Remington.
.338 is the British armed forces first long range large calibre rifle made by accuracy international, it is commonly know as the Arctic Warfare Super Magnum (AWSM) or has the military designation of L115. It was trialled against the Barrett and the PGM Industries Hecate, amongst others. The AI .50 only arrived for the last part of the trials in Alaska. The trials were pretty long and involved quite a few enviroments rangeing from the UK, through Brunie, Kuwait and Alaska. It has now seen active service and proved itself superior over range than the AW and the L96.
The military do not refer to .308 or .223, they are both referred to as 7.62mm or 5.56mm. The first has a cartridge case of 51mm in lenght (just so that it is not mixed up with the Kurz version with the 39mm case as used in the AK series) and the second has a 45mm Cartrdige case. They are however the same round in basis as thier civilian counterparts.
7.62mm is still in service with the American forces on the M60 as well as the Modified Remington M40A* variants, the M24 sniper variant and the variant of the M21 called the M25 (light sniper rifle).
The major difference for anyone using a large calibre (.338 or .50) is the stability of flight over range due to the weight of the round. To give it a flatter trajectory they have fitted the projectile to a monster casing with a lot of propellant, obviously power and weight is a trade off to get the best result, this is why people use them for extreme range shooting.
If you shoot a lot you get the bug to push your limits (you want to shoot further and more accurately), when you reach a certain range with .308 / 7.62mm they no longer cut the mustard and so you have to change to a tool that can, this is where the long range large calibre rifles start to come into play and @1000 meters a .338 holds the same kinetic energy as a .50. That is a lot of punch for a little rifle.
To demonstrate the difference in weight, the weight of a L115 is approx 15lbs (14.99 actual) without scope, the weight of the PGM Industries Hecate II is 30.36lbs and the weight of the Barrett M82 is 32.5lbs.
If you now think that the heaviest of the remington 700bdl family weighs in at under eight pounds you start to get an idea.
These rifles are large and heavy to give them stability, hence they also have bipods and butt spikes (in some cases), they are designed specifically for long range shooting and pushing your limits.
Believe me when I say these are not the largest out there, there are things like the Mechem NTW-20 and that is a real beast