I bought a S&W 25-5 once that looked like a smoothbore.
It took 4 Outers brushes and 3 movies to get the lead out. As long as the brush is a little bit harder than lead, it will get there eventually.
Complete thread:
- removing leading - 
bj, 
2017-07-30, 19:32 
- Nothing works fast or easy enough... - Hobie, 2017-07-30, 19:35
 - I bought a S&W 25-5 once that looked like a smoothbore. - Andrew, 2017-07-30, 20:32
 - removing leading - Sarge, 2017-07-30, 21:26
 - Lewis Lead Remover - Murphy, 2017-07-30, 22:29
 - Chore Boy - 
Jhenry, 
2017-07-31, 06:57
- 10-4 on the Chore Boy - Murphy, 2017-07-31, 21:09
 
 - removing leading - Jared, 2017-07-31, 09:33