Ring-around-the bolt face.

[coyoteking]

I posted a thread in the gunsmithing section about this but got no real answers. Any ideas?

Re: shiny ring on bolt face.

Is this a headspace issue?

There’s no dimpling or pitting or scorch marks so I don’t think it’s from gas escaping around the primer. I’ve never had any pressure signs on my brass, never a blown or leaky primer and never any problems with extraction or sticky bolt lift.

When I run my thumbnail over it I can’t feel any raised marks or indentations.

Its a Kimber hunter in 280AI. My loads are right at book max, using Nosler brass and I bump shoulders back .002” with a Redding body die.

 

[coyoteking]

Here’s a picture of the bolt face.

 

[adamg]

Photo isn't showing for me.

I think all my rifles have a ring between the firing pin hole and the outside of the rim head. I imagine that's what your photo is showing.

 

[dead meat]

Well there is your problem, it's a Kimber. Buy a Salvage. Seriously though don't worry about it, if your loads are safe it is not a problem. Like adamg my rifles also show this polished ring on the bolt face.

 

[IvoB]

as I wait for my COVID results you indicate right at max - are you sure that they are not over? Your assuming that your weighing and scale is 100% accurate - too much neck tension can also cause pressure spikes - can you eject the spent rounds like factory rounds - just points to ponder

 

[pacobillie]

From the edge of the primer pocket contacting the bolt face upon ignition.

 

[Philthy1]

It sure looks etched from primers. It's consistent all around though. Gas etching should be less "consistent looking"

 

[Ashcroft]

A more highly polished bolt face would hardly show these marks. I'm surprised that a Kimber bolt face is so poorly finished.

 

[6MT]

…..

 

[Philthy1]

280 AI is a relatively high pressure round to begin with, so you may be running a tad hot....but I have no doubt the rifle can handle it. I also have the same ring on a number of rifles.

 

[Workin Man]

Am I the only one seeing two rings in the picture? I see the brass coloured one, and a second ring, slightly smaller in diameter and black or blue in colour. It doesn't go all the way around. Starts at about 11 o-clock and runs clockwise to the ejector groove. I have no idea of the cause, just wondering if anyone else noticed it.

Jim

 

[coyoteking]

Thanks for the replies. I’ll maybe back off a tenth of a grain on my load.

It’s funny, none of my savages or Rugers have this ring, my Remington 783 in 223 does have it, but I do run a spicy load through that rifle.

 

[Longwalker]

Backing off "a tenth of a grain" is meaningless. It won't change pressure generated by the cartridge more than normal pressure differences caused by variations ambient temperatures. Or variations in neck tension, or variations in a few other things. Drop at least a half grain to a grain if you feel the load is over pressure limits for your rifle. Or a grain.

 

[bigedp51]

coyoteking

Do you feel any heavy bolt lift after firing or if you chamber the fired case is the bolt hard to close. I'm trying to figure out why the rear of the case is rubbing the bolt face.

The case stretches to contact the bolt face when fired and then it should spring back. I wonder if you bumped the shoulder back a little more if the rear of the case would press on the bolt face and rub.

With what type of comparator did you measure the fired case with? I also wonder if when the cases were made if forming the primer pocket caused a bulge around the base of the case just outside the primer pocket. Meaning the base of the case is not perfectly flat and the resized case needs to have the shoulder bumped back a smidgen more to keep it from rubbing.