Was cleaning a 522VIPER for friend.
Wet the brush and pushed into bore breech-end,
pushed clear past muzzle and reversed the stroke.
On the fourth stroke, the bore brush pulled from crimped socket of thread adapter.
About eight inches from muzzle.

Went to hardware store and bought a socket set screw in 8-32 thread, screwed into SS one piece rod, with socket reversed, as there is a small conic depression on working end. To try and keep the rounded lop centered as I pushed, to avoid jamming the rod and brush wire end loop to the side of barrel.

Added few drops of oil [Marvel myster fluid] down bore- breech, inserted one-piece rod into muzzle,
laid exposed rod on flat surface and rod handle into corner of garage stud and wall interface, and slowly applied force to VIPER action and barrel.
Came out "slicker than snot"!!

An alternate rod would be the GI bore rods for the 5.56 rifles.