Another week, another buzz-worthy pair of casting scoops for Sons of Anarchy Season 6.

The FX drama announced yesterday that C. Thomas Howell (Southland) and Steve Howey (Shameless) will both come on board in key roles this fall.

Howell will portray an ATF agent with questionable motives, while Howey will play a Las Vegas biker who comes into contact with SAMCRO.

Along with a returning Jimmy Smits and Donal Logue, these actors join an impressive guest star list that includes CCH Pounder as a district attorney and Kim Dickens as a Madame.

Sons of Anarchy Season 6 will kick off in September.

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.