It depends on the round. Handgun rounds will be based on handgun barrel lengths. Rifle rounds based on rifle lengths.
22lr stands for 22 long rifle, so rifle fps calculations and not all the powder burns in and handgun barrel so they are slower. This is part of why 22 silencers get so dirty so fast and are such a pain to clean.
I still need to build myself a blackout upper, this conversation is giving me an itchy credit card. I will say that 556 out of a short barrel is loud as hell even with a silencer.