Silly firearm props
The rifle silencer had a muzzle brake incorporated into it. Very few silencers have this feature and it is normally for very heavy recoiling firearms like those chambered in 50 BMG. Since he was using (per his voice-over) subsonic ammo, he would not need such a feature on the silencer which would only lead to an increase in noise.
His pistol silencer was actually a muzzle brake. They make the firearm appear to be much louder to the shooter and those standing to the side.