actually they're not. I was going to put my nano extreme upgrade kit into my epiphany and noticed the spring didn't fit so i picked up an ionfiring can (yes i have those laying around) and noticed a difference of about 2mm in diameter. The piphany firing can is smaller.
yup, the epiphany can should be smaller. I don't have a stock ion can, but when I switched from the epiphany can w/ no insert to a Warrior can, I had to drop my pressure.