Check Saubier.com for info on the mod. You'll need a magazine box with the large spacer also. Just a heads up, I have two original .17FBs, a Model 7 and a Model 700 with all original internals and neither one feeds worth a crap.I've been waiting on a fireball follower from PTG since February and my patience is wore out. I remember reading someone here has modified a 223 follower to work and wondered if someone would post some pictures and directions so I can finish this project up. Thanks.