Reaming cylinder throats leaves the finish deeply scratched with tool marks and you have to go behind the reamer with abrasive to clean up the tool marks, now your throats gets bigger than what the reamer cut when you use the abrasives so it then becomes a guessing game, exactly what the finished diameter will be by the time the tool marks are gone.
The Sunnen hone is a precision automotive hone designed for fitting wrist pins and pistons to connecting rods allowing the user to achieve extremely precise fits with less than .0001" tolerance. Used with pistol diameter mandrels the way it locates itself in the cylinder throat keeps the tooling square and concentric with the centerline of the hole, it will round egg shaped holes, it will make barreled holes parallel, a lot of cylinders the metal gets flame hardened by the intense heat and then cooling from firing cycles and these throats will turn out belled like a funnel pointing outwards, Not only does the flame harden the area of the throat directly in the path of the flame, the repetitive thermal cycles can also cause the metal to contract over time, making the throat diameter smaller on the entrance than the exit. The Sunnen hone operator can make the hole parallel by riding only the tight portion with the hone, and keep it parallel during honing.
The number one main reason I switched to using the Sunnen hone exclusively is because the heat treatment in the long steel rods Ruger uses to make cylinders is all over the map. It changes hardness in a seemingly random fashion, I have encountered quite a number of Ruger 45 and 44 cylinders with 3 throats that cut easily with the throating reamer, then the 3 remaining throats the reamer will be excessively hard to turn, the reamer will squawk loudly when you turn it, and it will feel like you are about to twist the shank right off the reamer because the metal in this throat is a lot harder than the other throats on the other side of the SAME cylinder.
Other cylinders are much more consistent in temper and with these cylinders, throats will ream much more predictably and the throats will be more of a consistent diameter. The throats that are harder, will finish smaller diameter than the throats that cut normally, so now you have inconsistent finished diameters because the size of the bore the reamer cuts is totally dependent on the hardness of the metal you are cutting with it. Harder metal makes the reamed throat come out smaller than a cylinder with softer metal. Quite common with Ruger SA cylinders.
Enter the Sunnen precision automotive hone. It is a stepless system so there is no defined stops or notches or whatnot, and it will make all the throats the same diameter regardless of metallurgy of the parent metal. And it's nicely polished to 800grit when finished! A reamer just can't do what the Sunnen hone does, you don't have much control with a reamer, you are at the mercy of the temper of the steel in the cylinder. The Sunnen hone is not hampered by changes in temper. It will take longer to hone a harder cyinder throat, it slows the hone down but you would never know in the finished throat because they can be held within +-.0002" of each other, and in many cases +-.0001" throat to throat tolerance can be achieved given a bit more time and patience at the hone.