Bellchambers played 16 games in 2012 – the most of his five AFL seasons – but shared ruck responsibilities with Patrick Ryder and veteran David Hille.
Hird said the 23-year-old was ready to hold down the position full-time after a strong pre-season.
"I think Tom Bellchambers is training very well and is looking to take the No.1 ruck mantle at the moment," Hird said.
"We've got good back-up in David Hille as well so Tommy's really been outstanding with his pre-season so far."
Hille had an injury-interrupted 2012, in which he played only nine senior games. The 31-year-old signed a one-year contract extension at the end of last season.
Meanwhile, Hird denied the Bombers had shifted away from the off-season philosophy of last season.
Captain Jobe Watson last week noted a number of players had focused on becoming "lighter" with the push to an endurance-based game, but Hird said it was part of the long-term plan.
"Pretty much most of the guys are the same weight they were last year, they're just able to handle it better because they're a year on," Hird said.
"We've trained a bit harder and we've run a bit harder than we did last year but that was always part of a program in building up over three or four years with players."
Follow Callum Twomey on Twitter at @AFL_CalTwomey.