In Iraq and Afghanistan, the troops have been finding that, when it comes to bullets, bigger is better. The .50 caliber (12.7mm) machine-gun, and the single shot 12.7mm Barrett sniper rifle, have been very useful. Both are very accurate weapons (in the hands of trained and experienced troops), and the heavy .50 caliber bullet will stop most threats (especially suicide car bombers.) At checkpoints, there are lots, probably hundreds, of suicide car bomb attempts you never hear about, because a .50 caliber machine-gun, or sniper rifle, took out the bomber. Even though the suicide car drivers have taken to wearing protective vests, and even armoring parts of their cars, that doesn't stop those .50 caliber bullets. The M2 ("Ma Deuce") machine-guns are often equipped with night sights, for many suicide car bombing attempts are made at night. Ma Deuce with a night sight and an attentive gunner is usually the worst possible news for a suicide car bomber.
Interestingly, the Iraqis never seem to learn about the effectiveness of the .50 caliber weapons. The .50 caliber sniper rifles regularly hit targets, with just one shot, 2,000 meters away. Iraqi terrorists planning can often be quite thorough and meticulous. But the long range and hard hitting power of the weapon continues to surprise terrorists moving about, believing they are out of range.
Even the 7.62mm snipers have continued to catch surprised targets (at up to 800 meters.) The Iraqi idea of a "sniper kill" is usually at ranges of less than 200 meters. The concept of longer range shots has not yet become accepted among them.