I received my 4" x 1"x 0.625 bucking bar today and I was blown away what a difference this makes. Not only is it easier (and a lot more comfortable) to use but the quality of the shop heads is also improved. You get a satisfying feel of the rivet tail collapsing and forming the shop head.. I want to send my steel bars to the smelter now. Thanks everyone for the recommendation!
The 4" x 1"x 0.625 bar (referred to as the snickers bar) looks like it would work for most situations, but for $70 I just ordered another bar that is 2" x 1.5" x 0.625" (referred to at the brownie bar). I think the brownie bar will be better suited to get into rib flanges. Anyone else have one of these and if so, do you find it useful?