I shoot centerfiew so this does not apply to rimfire.
I take a cartridge and remove the bullet. Then I empty the powder. Next I ca ber the casing and fire gun to set off the primer. Then I remove the primer. Then I clean the casing up and reinsert the bullet. I end up with a dummy cartridge that has no matador where the firing pin strikes.
I'm hoping you meant $3.50, not $350 YIKES!
I use them in my K-22 Masterpiece