Polishing a new chamber

[Rprecision]

The last 3 rifle's I chambered, both with SS and CM barrels, were left raw as the finish reamer left them. I have yet to encounter a problem with this method.

I have been reading some on the topic of polishing chambers. There seems to be 2 schools of thought about the topic. To be clear this is not discussing trying to eliminate dimensional problems such as pitting, scoring, etc. This is how a new chamber is finished, primarily for a bolt action rifle.

1. Leave it alone. This maintains the tightest dimensions. Break the sharp corners at the entrance, but no internal polishing is done to the chamber wall.

2. Polish it to varying levels ranging from very light to mirror polish. Those of a benchrest persuasion tend to favor a high polish. Others a light polish to break the smooth surface left from reaming.

The main discussion surrounding this topic is the relationship between the brass case and the chamber, specifically how well they grip each other during firing. It is proposed a medium or course polish leaves a rough surface for the brass to grip. This in turn reduces bolt thrust which is safer and improved action longevity. Alternatively, its argued a mirror polish has more grip, is more attractive, improves brass life and so on. There is clearly a broad range here

I have never polished one. I am considering these philosophies but dont have any experience polishing. Im inclined to try a medium scotch bright IF I decide to try anything.

My application is hunting guns, match and target guns.

What do you do and why? What can you share, suggest, etc.

Thanks

 

[J E Custom]

To perform it's best a chamber should have a very smooth honed looking finish.
With the correct spindle speed and a good sharp reamer this is the finish it should leave. Much like the cylinder finish on an engine, the honed look is in my opinion the best. It does what it is supposed to when fired. It allows the case to grip lessening
bolt thrust and increasing case life buy not allowing the brass to move around during firing.

If it is dimensionaly correct, it also extracts well. polishing only makes the person feel better that he hid the poor work he did. It is common for some smiths to use a reamer to long/to many times. so some polish instead of replacing or having the reamer re sharpening.

A bright shinny finish doesn't hold the case in place and produces more bolt thrust.
the proper finish is also proof that you cut a nice chamber. Polishing a chamber may help to chamber a round but it does nothing for the case.

In my opinion there is no reason to polish a chamber and the risk of altering it is great.

J E CUSTOM

 

[Danny1788]

I use 320grit emory clothe 1" wide wrapped around a plastic bic pen body, slit the end and wrap with the emory around it. I soak the emory in my flush system oil. turning the lathe at 600RPM I run it in with light pressure back and forth a few times, just a light cross hatch pattern. I only do this to break the "Glaze" the finish reamer leaves when I chamber with my pressure flush system. I haven't had any issues with this process and have always done it like that. Ive never tried to polish a chamber maybe I will try that to test if its any different.

My thought process was that this helps with bolt trust but never having tried anything else I don't know if it helps or not. Sorry I cant give a more info hopefully others will reply and we can discuss further.

 

[Mram10us]

You'll hear a lot of "best" ways, but there is no consensus nor proof one is better.
That said, I take Danny's approach, but add in 600 with oil after and finally red scotchbrite. I want my chambers to look like jewelry if I'm going to put the time into dialing in and making it as perfect as I can.
Try them all and settle on what you like. It would take you a long time to throw your chamber off with 600 grit or scotchbrite Do it to the outside of a piece of stainless for a test