A frequently asked question on suppressors is if they will slow down your bullet. This is probably due to video games and antique suppressor designs that might have actually done so. But the reality is that you get higher velocities with a suppressor.
Here is a comprehensive video showing .22LR, 9mm, .300BLK, 7.62x39mm, .223, .308 and .338 Lapua being chronographed with and without suppressors:
The difference was somewhat negligible being an average of all calibers (including the .223 which actually decreased by 11FPS within the 5 tested rounds) of 13FPS increase. If you were to leave out the .223 which threw a wrench in the test the average increase would be 18 FPS. Still, hardly enough to come into play until you reach several hundred yards out. But it does prove that a suppressor will increase velocity and not decrease it.
The velocity results, mostly measured with 5 rounds without a suppressor, 5 rounds with:
|Average (no 223)||+18|