"Sub-sonic" 9mm ammo

I keep seeing ammo listed as "sub-sonic". The velocity ratings all seem to be in the high-900 to mid-to-high 1000 fps range¹, which so far as I know is normal for center fire handgun ammo², so is the addition of "subsonic" to the description of the load marketing's answer to the proliferation of suppressors?

I once spent a very frustrating range session with what turned out to be slow .22s which would not reliably cycle a Ruger 22/45, and another with a Grandfathered Thompson M1928A1, one of the few grandfathered full-auto firearms in WA, which would not cycle WWB range ammo, so maybe I'm overly concerned with velocity.


1. The speed of sound being 1125 fps at standard temperature and pressure, which is about all I remember from high school physics, alas.
2. Ignoring hot loads, especially for .357 Magnum, etc.

Don't know why some ammo manufacturers add that but the 158gr prvi is pretty good for subsonic. I've shot it out of a 19 and it was pretty quite in comparison.

Pretty much all 147 and heavier 9mm ammo will be subsonic at standard factory pressures.

115 and some 124gr 9mm ammo is supersonic or flirting with it at standard SAAMI pressures and definitely at +P.

In 22LR ammo, 1050 or less is considered subsonic which I would think would apply to any ammunition.

Unfortunately I lost my notes on the subsonic 223 loads I made last year but the load I ended up with averaged 1035 FPS IIRC. At 4300' and 70ish degrees, it was subsonic based on what my ear (through electronic muffs) was telling me. I can't remember the speed that I started to hear the supersonic crack but it wasn't much faster than that.

Barrel length will greatly affect the velocity of ammo/what is printed on a box. What may be subsonic in a pistol could go supersonic in a rifle/carbine.

IOW: Marketing.

Or "probably marketing".