Wow. I'm surprised. Those tools marks are not mistakes !

When you get serious. You buy pin gauges to measure your cylinders. Pin gauges tell you immediately that the cylinder diameter is different at each end.
The diameter of the brass is larger than the bullet diameter (obvious). The cylinder must account for this by narrowing at the exit hole.
The brass must fit in the cylinder so that it doesn't split when fired. Poorly constructed bulged brass not fitting is the first time many shooters notice that size matters.

At the other end, the exit hole (chambers, throats)of the cylinder is machined to ensure the bullet doesn't wobble. It can be too tight or too loose. Too tight and you swage your bullet down to where it may allow gas to escape and lead the barrel. Too loose and your accuracy sucks. Tight can be fixed. Loose can not.

I've seen several over the years where someone wanted to make the cylinder the same shiny through out. They polished it until they lost the tightening at the exit hole. They lost their accuracy forever with that cylinder.

Handloaders use pin gauges to measure and select the correct size bullet for the cylinder exit hole and the barrel groove diameters.

Prescut
Difficult extraction of brass can occur when the cylinder size allows the brass to expand when fired; Goes in easy, comes out tough. Difficult extraction for a handloader can mean that the load is too hot.