Fairly certain that is just an error in the title. I believe most listings are generated procedurally and at some point the CB from the model number was interpreted as cylinder bore and added in. There really isn't a context in which it makes sense otherwise. If it implied the lack of a choke/constriction in the barrel as seen in shotguns, then I suppose nearly every handgun or rifle would be "cylinder bore".

John, I'm pretty sure this is a typo on buds end, I know they have a bad habit with typos. I've never heard the term used for semi automatic pistols and even Googling it can't find any answers. So my best guess is it's a typo. Hope this helps.

Thanks for the added info. Good luck.

John, I am not familiar with your previous question, but thank you for the info. Have a great day!