My MP5SD3 has an integral suppressor, but hey it gets hot after a couple mags in full auto.
I have an AWC suppressor that mounts on the 3 lug barrel of my MP5A3.The thing can stand some pretty serious full auto firing.Five mags in 3 minutes is about the limit of the system.Do you reload your sub-sonic ammo?I found that 3.3 to 3.4 grains of Win 231 behind a hard cast 147 grain NEI bullet works best.Cheap to shoot too since I cast my own bullets.