Possible chamber issue?

BradMacc82 · Dec 21, 2014

Re-barreled a rifle to 260 Remington, barrel is a 26" Shilen stainless.

Towards the end of my shooting session today, noticed that the bolt was getting tough to unlock and extract the spent casing. When I did finally get the casing out, I noticed these horizontal rings going around the entire case wall. (Photo isn't the best, but you should be able to make out the rings.)

View attachment 139443

The spent rounds showed no evidence of being over-pressure, and the rifle was shooting consistently.

The barrel has less than 300 rounds down the bore, and this is the first time it's exhibited those rings on the spent casings.

Any ideas??

SuperMag · Dec 21, 2014

Have you looked in the chamber to see if perhaps the chamber was not properly finished (do you see ridges or marks in the chamber bore that match the ring marks on the spent cases)?

BradMacc82 · Dec 21, 2014

I took a little piece of plastic tubing and ran it up and down on the chamber walls, can feel slight machine marks.

Kind of disappointed in that, figure a $300+ barrel would be finished a bit smoother.

E.Shell · Dec 21, 2014

It would seem to be a little rough, but the fact that it ran OK for a few hundred rounds means something is else changing. Freshly machined metal tends to get smoother with wear, not rougher.

I'd suggest cleaning the throat thoroughly. The slower powders used in the .260 often leave a hard carbon ring that will raise pressures as it accumulates. 300 rounds with a 90% effective cleaning regimen is about right to start seeing problems. Pressures are not yet excessive, but increasing enough to interfere with the cartridge case's release from the chamber. You should be able to feel a roughness in the throat with a tight brush that will abate as the brush moves down the bore into areas less fouled. Clean until the throat feels smooth again.

ETA: "...toward the end of my shooting session..." is another indication of this.

BradMacc82 · Dec 21, 2014

All rounds were loaded with Varget, 39.6gr charge.

I cleaned the hell out of the chamber, pulled everything apart to get a better look into the chamber as well. Reset the headspace and then re-verified headspace after the barrel nut was set to 40 ft./lbs. of torque.

BradMacc82 · Dec 21, 2014

Ed, you sir are a wealth of knowledge.

I used a slightly larger brush than I normally use, and sure enough - there was carbon in the throat. After a few passes with a larger brush, it feels smooth.

I guess there's a bit more to the 260 cleaning regimen than I thought...

**A test fire in the morning should give me some answers too.

BradMacc82 · Dec 22, 2014

No improvements.

Pulling the rifle back apart, I'll try to get Shilen to take a look at the barrel when they open again on the 29th.

Love the accuracy I got out of the 260, but it's fought me every single step of the way.

BigDaddy · Dec 22, 2014

While your are there, locking lugs like to be cleaned and lubed.

BradMacc82 · Dec 22, 2014

Done and done. Lugs were cleaned before the barrel went in, and every time I've had the barrel out.

Just for shits & giggles, cleaned everything back up and reset the headspace - yet again.

Closed on a Forster Go gage (just a touch of resistance on the very bottom of the throw, set to minimum headspace if I understand everything correctly). Less than 25% of a throw on a Forster No-Go gage.

Tried some of my pre-fired and sized brass, none of it will allow the bolt to close. Think it's safe to say that something in my reloading process is out of whack and is partially or completely to blame.

Now I got to figure out what...

BigDaddy · Dec 22, 2014

BradMacc82 said:
Just for shits & giggles, cleaned everything back up and reset the headspace - yet again.

20 years ago, I hunted with guys who had Jarrett switch barrel rifles, based on Rem 700's. They did nothing to headspace, when they switched barrels.

"yet again" sounds like you have done this more than twice? I don't know enough to say more, but if head spacing does change everytime you screw in the same barrel, then switch barrel Rem 700's are a fairy tale.

BradMacc82 · Dec 22, 2014

This one's a Savage action, so just a slight twist on the barrel while tightening the barrel nut can affect headspace.

E.Shell · Dec 22, 2014

Surprised that wasn't it. Are you neck sizing?

BradMacc82 · Dec 22, 2014

E.Shell said:
Surprised that wasn't it. Are you neck sizing?

I was attempting to full-length size, since my sizing/decap die was a FL. (Hornady Custom Grade)

But for some reason, the Hornady die isn't playing nice with the Lee shell-holder, my sized brass - I can't close the bolt on.

I've tried adjusting the die, and can't seem to get everything to play together...

Sticky · Dec 22, 2014

Are you getting a cam-over on the press at the end of the downstroke? Most dies want to have contact + a quarter turn or so to ensure the press cams over and properly sizes the brass when full length sizing.. A chamber gage will help you if you can find one for the 260..

BradMacc82 · Dec 22, 2014

I've tried camming over per Lee's directions, I've tried following Hornady's directions for the dies. And different points in-between.

Still can't close the bolt on the brass.

BradMacc82 · Dec 22, 2014

Well fvck me sideways.

Gave the die an extra HALF turn, and got a piece of brass sized to where the bolt closes as it did on factory brass.

Sticky · Dec 22, 2014

Think you are onto something now... :thumbsup:

outrider58 · Dec 23, 2014

so, i'm lost here. what was causing the impressions on the cases? overpressure? caused by a short head space? or by brass being too long? long in the shoulder? too long in the neck?

BradMacc82 · Dec 23, 2014

outrider58 said:
so, i'm lost here. what was causing the impressions on the cases? overpressure? caused by a short head space? or by brass being too long? long in the shoulder? too long in the neck?

This is just a theory, but I'm leaning towards a beautiful display of my ability to F up even a wet dream.

Between the carbon ring in the throat, my sizing die being out of whack, and the headspace possibly being on the tight side - voila.

OAL length on the brass was spot on, but the shoulder hadn't been set back enough - combine that with the carbon ring in the barrel that was gradually building up, and there we go. Raised pressures just enough to pick up the minute machining marks on the chamber wall and effect extraction.

The primers showed no signs of over-pressure - perfect radius, just a smidge of flow around the pin strike.

I'm not a gunsmith (clandestine) or a rifle expert (E.Shell), so my theory could be on-track or completely off, but that's where my mind is going.

**This isn't the first time I've looked to be a complete cluster fox-trot on the forum, and probably won't be the last time either.**

Sticky · Dec 23, 2014

Look at it this way... At least you are sharing your experiences, good and bad, with all of us so hopefully some of us will learn from them and not repeat them.. yes, we get egg on the face at times, but at times we come out beaming too.. :lol2:

Possible chamber issue?

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