the brand new accura has a finger removable breech plug. yours most likely used the tool to remove the breech plug.

just an opinion but none of this (entire topic) needs to be done to the breech plug on the cva rifles. Certain primers are just filthy and they leave a lot of "carbon"? build up in the flash channel. I used cci inline mzl primers today and the flash channel is super clean. with remington sts primers they build up crud fast and then i'll get one primer that goes plop and leaves a mess inside my rifle.

shoot your accura as it is and dont even worry about this vent liner stuff.