Well OK, they're trashed, but dry paper packing is about the toughest test medium you can use! At least they stayed together. I didn't try this with the RC4s, but suspect they would have disintegrated into a million bits.

Are you able to soak the mags for a couple of days in a tub of water till thoroughly soft, and try again?

BTW, can you still buy those Mirage slugs? If they are no longer available, you may be better off selling them to a cartridge collector and heading off to your local Brenneke outlet with the proceeds!