Wouldn’t kill you, or if it’s enough to do so, it wouldn’t be very fast. You need the potassium to be injected in a vein to work, intermuscular injections don’t absorb to the heart fast enough. It would, however, fucking HURT and cause potential necrosis and amputation.
Now imagine what botched lethal injections are like.
It’s a joke because it largely wouldn’t do anything but possibly make the gun a very little bit quieter for those around it while also making you completely unable to aim the thing because it obstructs the sights.