Pop quiz hot shot: Does a suppressor affect the velocity of your projectile?
The answer is yes, but not in the manner you might think. See, a suppressor actually increases the velocity of your projectile!
Yes, I know there are many Internet commandos that will tell you otherwise but the truth is that a suppressor marginally bolsters velocity.
The 2nd Marine Division Gunner in the video below will show you the difference in velocity between firing with and without a suppressor.
If my math is correct (no guarantees), based on his results, the suppressor he used on his M4 increased the velocity of the bullets by .59 percent, comparing group average to group average.
So, there you have it. The myth that suppressors slow your bullets is busted.
H/T: U.S. Marine Corps video by Lance Cpl. Timothy Lutz and Cpl. Clarence Wimberly