Bolt shows uneven firing pattern on face, and shines the brass case head upon extraction.

[Clownbuster]

Just like the title says. Brass has been fire-formed (two firings), rifle won't group better than 7/8" regardless the load, and I have a few of these calibers with established data.
Shiny/clean on one half, dirty and carbon fouled on the other.. What would cause this? Since none of my other actions exhibit this pattern from chamberings from the guys listed below, my first thought was the barrel wasn't correctly indexed and trued prior to chambering. Would that deficiency show up like this on the bolt face?

Would appreciate some meaningful input from some of the masters on here, thanks for any help @LongRifles Inc. @Frank Green @spife7980 @pmclaine @Supersubes

 

[wade2big]

I have the answer but you didn’t tag me in this thread like you did the others so I’m not telling.

 

[Supersubes]

What are the details on the parts? I think some of your terminology is off. Did the bolt face need truing? Is the black on the brassy side of the bolt face black from leftover original finish, or something else? Crooked bolt face perhaps.

 

[Clownbuster]

What are the details on the parts? I think some of your terminology is off. Did the bolt face need truing? Is the black on the brassy side of the bolt face black from leftover original finish, or something else? Crooked bolt face perhaps.

Terminus Kratos Lite Ti - I re-purposed the action from my 7PRC that was fired 100 rounds as a new rifle. The bolt face did not look like the current pic until it was re-chambered and fired as a 7mm-300WSM.

 

[Clownbuster]

I have the answer but you didn’t tag me in this thread like you did the others so I’m not telling.

Yeah but I thought of us, err, uhhh, I mean you, after I posted

 

[pmclaine]

The primer ring indicates to me that when it’s locked the case head sits square on the bolt face.

Kind of a lot of swirly machining marks on there. Cleaning my @LongRifles Inc. trued REM 700 bolt yesterday my bolt face didn’t have tooling marks like those.

I’m not seeing gas cutting or anything scary.

Possible with all the tool marks you get a little carbon cyclone under your brass. Hot gas cleans one side and as it cools you get carbon on the cooler side.

No clue but I appreciate your confidence including me with peeps that will have the answers.

Ps - Wades answer is always the cops are keeping you down.

My scope won’t zero

The cops are keeping you down.

My shit paper breaks finger when I wipe.

The cops are keeping you down.

We love him here because he is our own autistic parrot that gets it but just can’t stop playing those annoying bongos.


Now standby for a The cops are keeping you down rebuttal.

 

[pmclaine]

Here I am going to pull this out of my magic ass……

You might want to check headspace and see if you have some slop.

I don’t see primer gas jet cutting but how do the case heads look?

Is there carbon around the primer cup?

How good is your gunsmith.

Getting back in my lane now.

 

[wade2big]

The primer ring indicates to me that when it’s locked the case head sits square on the bolt face.

Kind of a lot of swirly machining marks on there. Cleaning my @LongRifles Inc. trued REM 700 bolt yesterday my bolt face didn’t have tooling marks like those.

I’m not seeing gas cutting or anything scary.

Possible with all the tool marks you get a little carbon cyclone under your brass. Hot gas cleans one side and as it cools you get carbon on the cooler side.

No clue but I appreciate your confidence including me with peeps that will have the answers.

Ps - Wades answer is always the cops are keeping you down.

My scope won’t zero

The cops are keeping you down.

My shit paper breaks finger when I wipe.

The cops are keeping you down.

We love him here because he is our own autistic parrot that gets it but just can’t stop playing those annoying bongos.


Now standby for a The cops are keeping you down rebuttal.

Not up here. I only preach that kinda truth in the pit.

 

[ACard]

What do the witness marks on the lugs look like? Even marks, lopsided marks etc...

 

[4O6shootist]

I removed all the dlc off the face of my terminus actions with a scotch brite pad, trimmed ejector springs down as they're too stout. Pretty heavy tooling marks you have going on there. If it's a new bolt, take a look at the dlc on the back side your bolt lugs. Wear marks should be even and consistent across all 3. Possibly may be loading one lug more than the other two upon firing putting stress and uneven pressure/load on that 1/3 of the bolt as the other areas aren't as supported. Don't ask me how I know to ask this since you said Terminus.

 

[spife7980]

Does it clean up?
How do the case heads look?
I’d try another brand of brass (good luck with that chambering lol) and eliminate that as a culprit as a first step I suppose.

 

[B'N'F]

Due to it being a spring loaded, plunger style ejector, you're seeing brass on that side because the ejector is rubbing on the case head (it will always make contact of course). Do you have photos of case head of some of your fired brass?

The above shouldn't really contributing to poor accuracy or otherwise, its mostly a mechanical artifact. The tooling marks might be accentuating what you're seeing as well, insofar that the brass is smearing into the peaks/valleys of the cartridge seat.

 

[Frank Green]

What does the fired brass look like and how does it measure?

What I'm asking here is are you seeing any bulge on one side (back at the web area) of the case more than the other side of the case?

Did you measure the fired brass for runout?

Measure/check headspace? You say it's rechamber job correct. You went from 7PRC to 7/300WSM. Was the barrel set back when the rechamber was done. Just looking at dimensions on reamer prints from the case head to the start of the shoulder the 7PRC is 1.819" long. The 300WSM case is 1.658". Just running the 7/300WSM reamer into the chamber so the headspace gauge works to rechamber it won't be enough to clean up the original 7PRC chamber. I'm pretty sure you would have to set the barrel back so it cleans up all the way unless I'm looking at the prints wrong or misunderstanding what was all done?

Got drawings of the actual reamer prints used to chamber the barrel originally and then the rechamber? So we know exactly what you had done. It wasn't a 7/6.5PRC chamber originally was it?

Need more pic's or the gun in front of someone that knows what they are checking/looking for. Not enough to go on right now.

Was the muzzle crown redone/touched up after chamber work? Wouldn't be the first time something like this was done and a center or something shoved into the muzzle end and have a negative affect on accuracy. That wouldn't explain the bolt face stuff you see.... but...?

Later, Frank
Bartlein Barrels