Emphasis on this, with the exception that they are not sold as caps, they are sold as feed test cartridges.
Read your manual to see if the manufacturer warns about dry firing, or OK's it.
If they warn against, strip it and pul the firing pin, or insert something for the hammer to strike rather than the frame or firing pin, like a chunk of eraser or rubber band.
RTFI! The aluminum dummy rounds are not for dropping a firing pin upon!
Store the chambers empty. No telling what the plastic is off-gassing, but if it is a snug fit, it will be pushing the oil layer away from where it makes contact with the chamber walls. Not like drywall anchors need to be inert, by any means.
Cheers
Trev
