https://apps.dtic.mil/sti/pdfs/AD0847383.pdfI have no experience, but this may help as a starting point.
IIRC, the Hi-Standard pistol of OSS & Powers/U2 incident is in this Frankfort Arsenal 1968 study. Page 35 as you scroll, but the original document is pg 19 (typical .gov
)
Money shot:
Silencing of the Hi-Standard barrel has been accomplished essentially by drilling the barrel and enclosing it in a silencing tube. The barrel has four longitudinal rows of "bleed" holes, 0. 125 inch
in diameter and spaced 0. 250 inch apart. The primary function of the holes, is reduction of the ballistic pressure which, in turn, also reduces the velocity of a supersonic Long Rifle cartridge below the speed of sound.
This design used bronze mesh as a heat sink & gas flow disruption & needed servicing/replacing.
Disregard if you already know: the 60gr Aguila subsonic are too long to be stabilized by standard .22 barrels & need 1/8 or tighter. I’ve known 2 guys—one just last week— who had problems with this round; I’m not sure if it’s still made.