Silly Quessy..?? Do fresh chambers ever "bed in/break in"?

[DenisA]

When a chambers cut, there are tiny machine marks around the shoulder for example. I guess like any machined metal surface, they'd be peaks and troughs under a magnification.

Being subject to the brass pounding against the shoulder under pressure when fired, I imagine the peaks could be flattened a little at the beginning of their life.

Is this a valid thought or a BS thought?

Why do people polish chambers?

I'm trying to nut out a quirk that I have with some chamber and cartridge measurements.

Cheers,

[Frank Green]

How bad are they? Can you post a picture? If it's just liney looking I wouldn't be to concern about it. Not going to effect anything. If the reamer tore during chambering it will have taken little chunks of metal out. Again accuracy wise and function wise it shouldn't hurt anything.

To answer your question though and in my opinion it's no. They won't break in or smooth out. The brass case of your ammo is way softer then the steel of the barrel. When you fire the round the brass case will form to the chamber and whatever is there.

When I chamber my own barrels I will polish the chamber but I don't hit the shoulder area or the case neck area. The shoulder area is where most rounds headspace off of. I might lightly touch it but nothing heavy. You start polishing to much you can change the headspace dimension you set the chamber to.

Usually the first thing that starts to go on the reamer is the throat area and the next in my opinion is the shoulder area of the reamer.

After every barrel I/we chamber we inspect it. Any sign the reamer is starting to leave a rougher finish or not cutting to size we pull the tool. The reamers will start to get build of material on the cutting/leading edges and also the edges will wear down etc....also I've seen brand new reamers that were not ground/sharpen properly and have different issues with how they cut. Weather it be to size or finish.

Later, Frank
Bartlein Barrels

[DenisA]

To answer your question though and in my opinion it's no. They won't break in or smooth out. The brass case of your ammo is way softer then the steel of the barrel. When you fire the round the brass case will form to the chamber and whatever is there.

G'day Frank, thanks for your reply. It seems pretty obvious and logical when you look at the impressions in the shoulder of a fire formed case.

Much appreciated,

[Frank Green]

Your welcome Denis!

To give another example. I have a 1903A3 Springfield rifle. All original. With hand loads it will shoot 3/4" groups at a 100 yards. There is a spot in the chamber towards the breech end. Something got in there and pitted/rusted it. The brass actually will flow and fill the void. The cases extract and gun functions fine. To bad though as the rest of the gun is stone cold mint! Made 7/43 and everything matches.

Later, Frank

[macguru]

I am pretty sure the chamber marks on brass make a unique 'signature' that forensic people can use as reliably as rifling marks on the projectile to identify a particular firearm. Or maybe they just look at the case head/boltface marks .....