Ive noticed my about 8 year old m70 featherweight 6.5x55 leaves nice tool marks on the shoulder of my brass.
Nice concentric lines/groves around on the shoulder of the brass case. Also a bit on the case sides

Anyone else notice this on a winchester?

Worn out reamer???

Heck, the bolt face is pretty bad with tool marks also but they have smoothed out alittle.


Im thinkin about puttin some polishing media on a fire formed case and polishing my chamber shoulder a bit.

My chamber is alittle ruff with tool marks compared to my other rifles.

Bolt lift is alittle rough even with low powder/pressure loads, im thinkin just from the brass hangin up on the tool marks .

quote:

Anyone else notice this on a winchester?

Worn out reamer???

I've seen it before....I don't like it but it don't really hurt anything...I'd leave it alone.....but polish it if you wish.....it'll take some doing to get the lines out.

If one feeds a reamer to it's destination and retracts it this happens sometimes. If one leaves the depth a few thou short and cleans the reamer and then makes a final finish cut this can be minimized....but a bit of emery on a stick after reaming at 500 RPM or so can remove them totally.

Hell,, if I put a big glob of course valve grinding compond on a brass case shoulder and ram it in there wit a drill It might become a bubba improved swede

I bumped the shoulder back with with my full length die on this batch of brass. Might of had a hot load on that brass. Now it chambers easyer

Think Ill leave the chamber as is. It aint that bad.

My Rem 700 ADL in 204 Ruger had that problem -- a tool mark that went ~30 degrees around the inside of the chamber about 1/4" inside. Probably a spot where the reamer picked up a chip or chipped a teeny bit.

The technique to use is called "Draw polishing"
What it means is that you want to polish in the direction you need the shell to "draw" as in in and out direction, rather than round and round -- which tends to encourage things sticking worse.

Grinding or lapping Round and round with something can end up hogging out the chamber, and leaving pretty much the same high spot as was there before. Don't use a dremel, grinder, or drill motor, as they take off *way* too much material and are impossible to control.

This draw polishing is done with a hand held cylindrical machinists stone ~220 to 300 grit whose diameter is slightly smaller than the chamber. They look kinda like a round pencil made of stone.

Go straight in-out-in-out (NOT round and round), and you feel the stone hit the burr as it polishes it down. It kinda feels like "swish griiinnnddd swish" Once you don't feel the griiinnnddd part as the stone goes over the burr -- you are done.

You might be able to get by with a small dowel with a little strip of medium-fine grit wet-dry sand paper on it.

Once the burr is down, polish the heck out of it with Flitz on a shotgun mop in a drill motor. Viola... no more burr, and you haven't messed up the basic geometry of your chamber.

Best regards

John