For many years I made my own dummy rounds by loading sized cases with a piece of plastic (to fill the powder space) and a bullet. I used pieces of nylon rod for primers to protect the firing pin. If necessary, I also ground off the section of rim the extractor would engage so the case would not be ejected when the gun was operated to recock the hammer/striker. In many "shots" fired in practice, I never accidentally loaded a live round (how?) or shot holes in the wall.
Jim
Jim