How exactly are we supposed to kill K9 dogs in COD MW2

Attach FMJ to the weapon you are trying to complete the challenge with. Then follow an enemy with your fire as they run for cover. Or otherwise try to get them behind cover once they are hiding. Often, you can easily spot someone behind a window or a wall when the barrel of their weapon is sticking out. Easiest to shoot through is sheet metal like the most walls on Scrapyard.

Both games implement some combination of or have variations for each of the following features:

• Scope sway
• Gravity induced bullet drop
• Bullet travel time
• Body posture
• Clothing (Ghillies)
• Tools

Battlefield:BC2

Scope sway

None. BC2 does not implement a "breathing" aspect for sniping. Thus your crosshairs are stationary unless you move them.

Gravity induced bullet drop

Yes. As range to target increases the actual point-of-impact of your round with relation to the center-point of your crosshair increases.

With very long range laterally moving targets you have to put their torso in the lower-left/right quadrant of the scope and fire to get a hit.

I feel that it makes stationary target sniping ridiculously easy compared to MW2, but makes it harder to hit moving targets.

Bullet travel time

Yes. You must lead targets that are in motion.

Body posture

You cannot go fully prone in BC2. You can only kneel.

Clothing

Snipers wear ghillie suits. Their utility can be limited since they cannot go fully prone. It is still useful in large bushes and trees though.

Tools

There are no thermal scopes, heartbeat sensors, AC-130's or other anti-sniper elements in this game.

Call of Duty:MW2

Scope Sway

Yes. MW2 implements a "breathing" aspect for sniping. Thus, when completely stationary your crosshair will bob semi-randomly. You can also "hold your breath" for a short amount of time which reduces the movement, though not completely.

Gravity induced bullet drop

None. Whatever is under the center-point of your crosshair when you pull the trigger is what gets hit.

Bullet travel time

Yes. You must lead targets that are in motion.

Body posture

You can go fully prone in MW2. This decreases scope sway and makes you harder to see.

Clothing

Snipers can wear ghillie suits. The suit must be unlocked. Different camouflage colorings can also be unlocked.

Tools

As a sniper you can unlock a thermal scope which makes sniping super easy-mode. However, you are also terribly vulnerable to things like AC-130's, Harriers, etc. unless you are using cold-blooded.