Check out Knifemaker/s posts on cutting the choke off..https://www.gatewaytoairguns.org/GTA/index.php?topic=180900.20
As far as the Monster design power wheel goes, it is a cnc machined piece of stainless steel.. 50 is ok price for it but I would contact mrshosted on AGN to see if he has any left..
...I am sorry about butting in your post !!!
About a half in or so on my .25 cal 700 mm liner. This is guess I can measure tomorrow for exacts.
make sure you mark the breech end so you don't inadvertently install it backwards at a later removal.