In terms of bullet drop, putting a suppressor on a weapon does not have a large effect. It can boost velocity by a small amount, or it can cause the bullet to lose some velocity, but it will not have a drastic change such as what happened in ArmA 2 from using SD magazines.

The drastic changes come from the type of cartridges that are loaded, not from the suppressors.

Agreed with Goose.
Suppressor by itself wont affect noticebly the bullet drop, but subsonic rounds (SD mags in ArmA2) do.

A supersonic round fired from a suppressed gun would only do the "crack" while passing near you, not sure if you should be able to hear it as a shooter but certainly the target should hear it

A suppressor only acts to dissipate the gasses that cause the crack, they /may/ slow down the bullet by a fraction of it's speed because of friction, but not enough to be noticeable.

Yeah I understand that, I always thought it would reduce muzzle velocity as well but apparently I was wrong.

http://www.youtube.com/watch?v=6dYX-h-5HDQ

Above is an FPSRussia vid of a 1911 with a suppressor/silencer. Skip to 1:10, it's attached at this point and he is firing regular ball ammo (not sub sonic crap). Rifles are affected similarly, just with larger equipment.

(thx FPSRussia!! ^_^)

A suppressor will give about a 20% performance increase on a pistol because it acts as a longer barrel, allowing more of the charge to burn. On a rifle it results in a negligible reduction in performance.

Closing as this seems to be a non-issue.