FX Can’t believe the sound difference

Not sure if it’s my tune or what is wrong. So looking at pyramid air the Panthera is 3 for loudness and the M3 it’s 4.

I have a Panthera compact 22 with the 380 barrel. I got it down to less than 50 on the reg and close to 500fps as I want to shoot in basement and it’s quiet.

With new M4 there are tons of used M3 for sale. I bought a M3 compact with 500 barrel for 1500 other day. So happy. The guy had it on a 18gr tune. So the first shot I tried was with 25.39gr Straton it went 750 ish.

Wow what a difference in sound. The M3 is so much quieter than the Panthera.

I’m sure it’s the barrel. But could my Panthera low tune be causing issues??? I still don’t understand why pyramid would say Panthera compact is quieter than M3 compact.