There are a few reasons to ream a cylinder throat. The most obvious reason is to correct an undersized throat diameter. Some manufacturers regularly produce their revolvers with cylinder throats that are smaller than the bore diameter. The problem with this is not only does it increase chamber pressure, but it isn't conducive to accuracy. When a bullet passes through the undersized cylinder throat, it is swaged down to the smaller size. The bullet is now undersized for the revolvers bore, leading to decreased accuracy and increased leading with cast bullets.

As well, some heavy bullets and LBT style bullets will not chamber in a cylinder with tight throats. This is quite common with LFN and WFN profile cast bullets. This was the very reason I started to do this work in the first place. My own guns wouldn't chamber 300gr WFN bullets.

Many shooter want to be sure that their cylinder throats are uniform, and like knowing that things are "right". Uniformity plays a large role in a revolvers ability to group. Persistent flyers can often be traced to one or two throats in particular that vary from the rest.

While we do not make any claims or guarantees of improved accuracy, it's generally the case. Like most things, some guns will greatly benefit from this work with major improvements, while with others it will not be as noticeable. I will say that in the several years that I've been doing this work, in terms of accuracy most guns benefited to some degree. Some did not. NONE have gotten worse.