If you are talking about the patent breech, IMHO, unless you are well experienced at removing oddball breechplugs, you best leave it alone.. :shake:
You don't need to clean the patent breech with a jag, clean it with a bore brush or a rounded breechface scraper, & then dry it with a patch on a slightly smaller caliber bore brush. You can oil the patent breech with a bore mop.
On some of these mass produced barrels, the breechplugs are put on by machine under tremendous torque, thus you may really skin that barrel up taking the breechplug out if you are not experienced to it. Some of them are put together under torque & locktite, etc. I would avoid removing it if at all possible.
Keith Lisle