John A,~ Like yours my .357-Magnum Handi Rifle has a very long chamber and almost accepts MAXIMUM brass. I considered the reamer idea once but I came up with something else instead. I bought Hornady XTP 180-gr bullets that have TWO cannelures and crimp in the bottom cannelure so the cartridge is just a little bit short of a MAXIMUM. There is a LOT of bullet outside the case. https://www.hornady.com/bullets/handgun/38-cal-357-180-gr-xtp#!/ Then I load to MAXIMUM data minus about 15% and it really launches them! And I believe I could load these even hotter should I want to.