I ran across an interesting comment in a really stupid article on subsonic rimfire: https://www.americanhunter.org/articles/2018/3/19/top-6-subsonic-22-lr-loads-for-small-game-hunting/

The really stupid article is in the NRA's American Hunter. In an article supposedly comparing the terminal ballistics of subsonic .22LR, the sound pressures are not reported and they use clay blocks to display wound cavity. Clay is a ridiculously unrepresentative tissue simulant.

But here is the interesting comment:

The common misunderstanding of Subsonic ammo is that until the bullet 's muzzle velocity is below abour 980 feet per second, the round will create a supersonic shock wave - even when conditions provide for 1100 fps being the threshold.
WHY?
When air encounters the front of the projectile it follows the curvature of the nose. As it splits from it's vector it must accelerate to cover the greater distance (over the spherical shape of the bullet's nose as compared to a straight line from the front of the bullet to the tangent ov the bullet's main cylinder shape. Averaging the velocity of of air over a bullets spherical front end as the bullet's vector airspeed is 1000 FPS we calculate:4 divided by 3.1416 X1000 which equals 1273 feet per second. By the same token that 1273 feet per second. AT the bullet's point the velocity of air will be 1400 fps or higher, but is slows to 1000 fps by the time it reaches the line representing the diameter behind the curvature of the nose. In the case of a 1000 fps velocity, only about 25 - 35% of the round's sectional area would be supersonic, and only for maybe 30 - 60 feet. At 970 feet per second, maybe 10% of the round' sectional area would be supersonic - an then only for maybe 20'. In my own testing the report of the 970 fps round was minimal compared to the 1050 foot round whose crack was very noticeable but much less than a 1255 fps standard V round. The funny thing is the 710 fps CCI round. It goes "click; thats all.
I use a Spectre silencer on a 10/22. It is very clear that either CC! Suppressor or Aguila sss60 are the only two rounds that really serve the suppressed shot without giving up kill power. The SSS60 is a keyholer but I find it carries accuracy most of 100 yards and obliterates whatever it hits while wobbling. My recommendation is to try both. The CCI will be the more accurate. It will kill at 100 yards, but the SSS60 packs more wallop; I believe a coyote meeting a 60grain slug at 70 yards better have a plan b.

This explains why CCI "Green Box" at 1050 fps is not labelled subsonic.

Anyone have success with Aguila subsonic rounds?

Faster twist rates are necessary to stabilize the heaviest bullets. A yawing bullet is likely to cause a baffle strike, potentially destroying a suppressor.  It behooves us then to fire the subsonic rounds without the suppressor to check for keyholing/yawing.
I did that through a pistol and a rifle, both with the standard 1-16" twist rate, and obtained gross keyholing with the Aguila SSS. Obviously I did not mount the can. A 1-9" twist is required to stabilize the 60 grain projectile of the Aguila SSS ammo.  Interestingly, even though the Gemtech Integral MIST-22 barrel, an integrally suppressed barrel for the Ruger 10/22 (and Ruger 10/22 clones), is intended for suppression, it has the standard 1-16" twist. Go figure.