[NYCSTRIPES]

Fist off, they are called Supressors, not silencers. Ammo choice is huge when firing a weapon with a supressor. If you fired standard high velocity 9mm ammo, you'll still get the sonic crack as the bullet leaves the supressor because the round is still travelling faster than the speed of sound. Want it to be quieter? then fire subsonic ammunition.
As for accuracy, the MP5 is an entry weapon, not a sniper rifle. Its meant to be compact and put lots of rounds on a man sized target in short order.
Need to fire it more accurately? Practice some more, they are plenty accurate out to 50 meters in the right hands. One must remember this weapon only fires pistol ammunition and must be treated like a glorified handgun. Albeit with the option for full auto.
I have fired them extensively and they are great weapons when one understands their limitations.
Hope it was at least fun to shoot.

The M4 with 3 shot burst is also something that required training to shoot well. Controlling anything that fires rifle ammo in a burst configuration is something that demands training and trigger time. Muzzle flip is more pronounced with a jump to rifle ammo. Learn to control the MP5 with burst first, then you may understand the M4 better later on.
Ken