A mod makes a noticeable, and several dB difference on a .22HV, as it does on centrefres, that's why people use them!
It goes a long way to reducing the propellant bang, just leaving the sound barrier crack.
I think we might have drifted off track a bit here. To the OP, as stated by Stavross, the RFD will write the ammo on your ticket, and no, you don't have to notify anyone when you buy ammo.