I don't own a 42 but do have a few 24's. When I was a kid I used some old started blanks behind a .22 cal pellet, made similar power to my Benjamin 342 but was silent. I never could find another tin of the same blanks and none of the other blanks I tried ever gave me the same results.
Last year I played with the idea again, curious now that I have chronographs, and used nail gun blanks.
The #2&3 worked and gave over 2000 FPS.
I wouldn't try it with anything but a single shot. Actually I only did it to learn something and stick with .22 ammo myself.
