There are enough old CoD-hands here, that I'm sure one of us has mentioned this already somewhere along the way, but it's worth reiterating either way;
Pick the gun to suit the map.
Picking a sniper rifle on something like Dome for example is going to end badly for you, unless you're a d1ck-scoper.
Any tight maps like Dome or Bootleg, you're probably as well going with an SMG, or a shotgun, although I steer clear of those myself.
Maps like Bakaara, or Mission, I like to snipe as there are some good long distance opportunities on those maps.
Alternatively, you find a lot of the time that specific weapons work to varying degrees on different parts of the main map, ie. Mission - some really long straights by the A and C flags, but stay away from B. Underground - lots of tight turns if you stay in the buildings or out and about around the train carriages, ie. use an SMG.
If you're insistent on running around the entire map then the best bet is to generalise, and there's no better class of weapon for doing that than the assault rifle.
Another thing - don't get obsessed with the weapon stats - or at least make sure you're not mis-reading them. It's easy to base your selection on 'damage', but it really needs the context of 'rate of fire' as well. It's possible that a weapon with a lower damage stat is actually more deadly because the rate of fire is so much greater.
All this being said though, you will find that your performance or experience may vary from game to game as the hosting on MW3 is supposed to rotate and not stick with just one person game after game. Hence, the performance may change from game to game equally.
Pick the gun to suit the map.
Picking a sniper rifle on something like Dome for example is going to end badly for you, unless you're a d1ck-scoper.
Any tight maps like Dome or Bootleg, you're probably as well going with an SMG, or a shotgun, although I steer clear of those myself.
Maps like Bakaara, or Mission, I like to snipe as there are some good long distance opportunities on those maps.
Alternatively, you find a lot of the time that specific weapons work to varying degrees on different parts of the main map, ie. Mission - some really long straights by the A and C flags, but stay away from B. Underground - lots of tight turns if you stay in the buildings or out and about around the train carriages, ie. use an SMG.
If you're insistent on running around the entire map then the best bet is to generalise, and there's no better class of weapon for doing that than the assault rifle.
Another thing - don't get obsessed with the weapon stats - or at least make sure you're not mis-reading them. It's easy to base your selection on 'damage', but it really needs the context of 'rate of fire' as well. It's possible that a weapon with a lower damage stat is actually more deadly because the rate of fire is so much greater.
All this being said though, you will find that your performance or experience may vary from game to game as the hosting on MW3 is supposed to rotate and not stick with just one person game after game. Hence, the performance may change from game to game equally.