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I have a Kel-Tec P17. It is a very nice pistol for the price. About the size of a Walther PP, but half the weight and twice the magazine capacity. So far, best groups are about 1.5 inches at 50 feet from a rest.

Kel-Tec P17 with optic and silencer.

Lightening cuts on P17 slide.

Mansfield Glock Yeet Cannon ....so tacti-cool.

I have a P17. Fun little pistol.

One of two Kel-Tec pistols I own. The other is a P32 which has been flawless.

Most .22 LR ammunition -- excepting primarily stuff advertised as "hi-vel" -- is subsonic when fired from a handgun. And provided you have a suppressor, it's easy to tell if your ammo is subsonic or not, even if you don't have a chrono.

The 'crack' of a supersonic bullet echoes off everything that gets in its way, and the echo is easy to detect if your hearing hasn't already been been overpowered by muzzle blast (which the suppressor prevents happening). If you don't hear the echo, that can only mean your bullet was subsonic. Either that or you're in the middle of the Bonneville Salt Flats and there's nothing for miles for it to echo off.

You might be able to hear it without a suppressor but with one it's really obvious, especially without earpro. Which is more practicable with a suppressed rimfire (which with subsonic ammunition is about as loud as a slamming card door) but I wouldn't recommend it with even a suppressed centerfire.

And keeping your bullet subsonic might be a little more complicated than you think because, strictly speaking, it's not about the speed of sound, it's about the transonic region. An airplane or a bullet will generate a supersonic shockwave as low as the critical Mach number, which is the lower threshold of the transonic region. And all shockwaves have an accompanying "sonic boom."

Testing done by "dean of silencers" Alan C Paulson found that bullets in flight always have an accompanying "crack" down to at least 0.8 Mach and sometimes to 0.7 Mach. So depending on the local speed of sound, bullets as fast as 880 fps are almost certain to make a "crack," and bullets as as slow as 750 fps might.

Truth be told, the actual "speed of sound" is entirely meaningless to a bullet. It's actually the transonic region -- which starts at the lower critical Mach number, which is ~20% below speed of sound and continues to ~20% above it -- that is responsible not only for the crack of the bullet but also for the instability encountered by some bullets when slowing to the vicinity of SOS.