1 in 28 should handle a fairly heavy bullet (and lighter ones too). You might want to check with Ed Huble about brass cases.
What will the chambers be reamed for, length-wise - 3"? The reason I ask, is that a 3" chamber will likely handle heavier bullets at a quite descent velocity. Of course, the longer the chamber, the lower the pressure at any given speed, using the appropriate powder, that is.