...I thought I had seen or read some place
about a tube you can put over the nipple and suck or pump water into
the barrel this way..Maybe it was something all together different..
That'd be the flush kit cayugad mentioned. The one I'm familiar with is the Ox Yoke Blackout flush kit. Your rifle would take the 6X1mm size. Or you can drill out the flash hole in an old worn outnipple,glue about a 2-3' lengthof aquarium tubing to it and have the same thing.