Weird markings on fired brass

[cast1]

Just finished my first build. 110 action, Shilen select match in 260 remington. Headspaced with Forster gauges. Bolt hangs about a third of the way through its arc on the no go gauge. My first five shots show concentric marks on the shoulder as shown below. It almost looks like there was a burr or nick on the reamer when it was made. The shoulder looks kind of funny too, almost distorted. Is this anything to be worried over?

http://farm9.staticflickr.com/8192/8123661427_9587d01d85.jpg (http://www.flickr.com/photos/54751114@N07/8123661427/)
2012-10-25_21-26-21_734 (http://www.flickr.com/photos/54751114@N07/8123661427/) by bsshep1 (http://www.flickr.com/people/54751114@N07/), on Flickr

[seanhagerty]

You might try cleaning the chamber with steel wool on a qtip thats chucked into a drill. just go at it a bit and then see what happens

[LabRat2k3]

Yeah there is something not right with the shoulder on that fired brass. I would suggest doing a casting of that chamber and check to see if it is in spec.

[FUBAR]

Better use another headspace gauge, looks like it's "bumping" the brass for you!

[barthowes]

+1 on the bumping brass. Looks to me like your headspace is on the small side and your "crushing" your cases. If there was a burr you would see it.

[Gmac5]

Was it a full charge or just a lite fireform ? If it was a lite load it may not have expanded the case enough. If it was a full or near normal load i think a chamber cast and a call to who ever chambered it is in order.
Gary

[Gmac5]

Forgot to ask is it 7.62 x51 military brass or 260 brass?

[FUBAR]

I have a old design 280AI, and if I use Nosler 280AI brass they have .014 more headspace, and I have to bump the shoulder back...if I bump too much they look sorta like your picture.

However the prior question about the brass is applicable...

[cast1]

Federal factory loads just to get on the paper and break the barrel in. I had backed off the go gauge just a hair before I snugged the nut down, thinking it might tighten a little when I torqued it down. I took it all apart and re-did the barrel install just that slightest bit tighter. I was more worried the first time about too much headspace vs too little. This is a pre fit from NSS.

[Gmac5]

Take a fired case and measure id , it may be lrger than you think

[MrMajestic]

Could the chamber have been damaged by leaving the go-gage in the chamber when snugging the barrel nut? Just thinking out loud.

[stangfish]

Take a picture of the chamber if possible and the picture of the brass and send it to Shillen.

[jonbearman]

Was this a pre-fit or did a gunsmith chamber it? If it is a pre-fit,send it back as it looks like the reamer was severly worn to me.

[ellobo]

Tightening the nut will back off the barrel a small amount. I don't remember how much. I think Sharpshooter can confirm this if he chimes in.

El Lobo

[cast1]

Re-did everything with the tighter headspacing and tried it again. Same result, only farther up on the case shoulder. I took a couple more pics:

http://farm9.staticflickr.com/8333/8129713788_8bc426e4df.jpg (http://www.flickr.com/photos/54751114@N07/8129713788/)
Default title upload by motoblur (http://www.flickr.com/photos/54751114@N07/8129713788/) by bsshep1 (http://www.flickr.com/people/54751114@N07/), on Flickr

http://farm9.staticflickr.com/8333/8129713782_8f7c0d25ba.jpg (http://www.flickr.com/photos/54751114@N07/8129713782/)
Default title upload by motoblur (http://www.flickr.com/photos/54751114@N07/8129713782/) by bsshep1 (http://www.flickr.com/people/54751114@N07/), on Flickr

You can see that there is basically a bunch of fine scratches on the shoulder and a positive ring around its diameter. It looks like a chip got stuck on the tooling and gouged out a defect. You can see the waviness in the photos. I thought I was buying the best that Shilen had to offer. I will contact them to see if they will make it right, but in my mind, something like that should never leave the shop.

[cast1]

It was a pre-fit.

[cast1]

Could the chamber have been damaged by leaving the go-gage in the chamber when snugging the barrel nut? Just thinking out loud.

Did not leave the go gauge in when tightening the nut.

[BillPa]

Tightening the nut will back off the barrel a small amount. I don't remember how much.

El Lobo

On the average .001"-.002" depending when the threads are tensioned, although I had one tighten up. Never quite figured that one out. :confused:

Whats bug'n me, in the picture the shoulder isn't fully formed and it appears to be a quite a bit of blow back on the neck,shoulder and the body. The bright ring on the shoulder looks more like it was wiped off than a mark on the brass. It has every indication of a light charge and/or excessive headspace-head clearance.

http://farm9.staticflickr.com/8192/8123661427_9587d01d85.jpg

It almost looks like when I'm working up the charge using COW and Unique to form improved brass and the starting charge is too low, rounded shoulders and blow back, the brass not expanding enough to seal the chamber.

At this point I'd do two things. First remove the barrel, clean the chamber them drop the GO gauge in and measure the amount of protrusion and second, make a chamber cast. The protrusion would verify the chamber length and the cast a visual verification of the shoulder.

Bill

[cast1]

Well I think I figured it out. Took the barrel off and shined a flashlight down in the chamber. The shoulder is very rough and is a mirror image of what I am seeing in my brass. Don't know how often this happens, but I figure if it's going to, it will happen to me. Just glad I didn't get a face full of hot gas. I will be contacting Shilen and Northland tomorrow to see how they will handle it.

http://farm9.staticflickr.com/8331/8133513968_da03f69d0d.jpg (http://www.flickr.com/photos/54751114@N07/8133513968/)
Default title upload by motoblur (http://www.flickr.com/photos/54751114@N07/8133513968/) by bsshep1 (http://www.flickr.com/people/54751114@N07/), on Flickr

[cast1]

Why are my posts having to wait for administrator approval? I have posted three other pictures in two posts and I get told they won't be visible until they are approved by an administrator. Am I on probation or something?

The problem is with the chambering of the barrel. I took it off tonight and sure enough it looks very rough down in there. There is a picture of it in one of the posts awaiting admin approval. Maybe it will show up. We'll see how it gets handled either by northland or Shilen.