Need help solving a chamber problem,... if possible

[Lefty Trigger]

I had a couple of barrels made with my reamer (6BR Norma) and after a few hundred rounds being fired I started having a very slight "sticky bolt". At first I thought my loads were too hot, they was near the top end, but after reducing them the problem remained. Well recently I annealed my batch of brass and I think the culprit of the sticky bolt can now be seen. This picture of my brass is 1 firing after being annealed, it has been tumbled. Notice anything weird....? I'm pretty sure my chamber has some radial scratches near the shoulder end. Any way to polish them out or reduce them? I think the fired brass is not sticking but "locking" into the scratches. Keep in mind this is very minimal sticking just a slight tap frees the bolt and it shoots awesome so I don't want to alter it in a major way so if it's not a simple fix I tolerate it till the end of barrel life and just move on.
BTW, you can not feel the marks on the brass and they wont catch a finger nail.

 

[DaveTooley]

Those rings could come from the chamber or your FL die. They wouldn't cause a sticky bolt. Likely the sticky clicking bolt comes from not enough chamber clearance. Easy fix just polish it out a few thou in the area of the case head. That is unless there is something going on with the FL die. I'll add brass work hardens during firing and sizing. The key is manage the size as it work hardens. Once hardened at a larger than desired diameter a FL die will just get it back into the chamber. The brass when fired goes to its larger work hardened diameter. Results in a sticky bolt.

 

[Lefty Trigger]

Those rings could come from the chamber or your FL die. They wouldn't cause a sticky bolt. Likely the sticky clicking bolt comes from not enough chamber clearance. Easy fix just polish it out a few thou in the area of the case head. That is unless there is something going on with the FL die. I'll add brass work hardens during firing and sizing. The key is manage the size as it work hardens. Once hardened at a larger than desired diameter a FL die will just get it back into the chamber. The brass when fired goes to its larger work hardened diameter. Results in a sticky bolt.

So this could be an indication of brass at the end of it's life cycle? I have new brass in reserve so I may try a few and see if they "stick" as well... will report back.

 

[DaveTooley]

It takes time for brass to work harden at a larger diameter. That's why chamber clearance vs brass diameter and FL die vs fired brass dimensions are important. I have brass that has well over 50 firings and will function in multiple chambers. It's all in the details.

 

[AlNyhus]

What Dave said.

Hard to say w/o having everything to measure and eyeball. Chambers can be too smooth and give you a sticky bolt feel. But again..it all depends on the details. -Al

 

[Ggmac]

Ive seen rings like that on barrel set back and not setting up correctly or using the wrong or no pilot . In your case it looks like multiple set backs , which I doubt .

 

[tobnpr]

Looks exactly like chambering artifacts to me...

 

[gunsandgunsmithing]

Looks exactly like chambering artifacts to me...

That's downright ugly

 

[Michael Huebner]

I had a couple of barrels made with my reamer (6BR Norma) and after a few hundred rounds being fired I started having a very slight "sticky bolt". At first I thought my loads were too hot, they was near the top end, but after reducing them the problem remained. Well recently I annealed my batch of brass and I think the culprit of the sticky bolt can now be seen. This picture of my brass is 1 firing after being annealed, it has been tumbled. Notice anything weird....? I'm pretty sure my chamber has some radial scratches near the shoulder end. Any way to polish them out or reduce them? I think the fired brass is not sticking but "locking" into the scratches. Keep in mind this is very minimal sticking just a slight tap frees the bolt and it shoots awesome so I don't want to alter it in a major way so if it's not a simple fix I tolerate it till the end of barrel life and just move on.
BTW, you can not feel the marks on the brass and they wont catch a finger nail.

I wouldn’t be putting new brass in either without some further investigation.

I think your best bet is have a look at both chamber and the die with a bore scope and see what is going on.
If you don’t have one hopefully you know someone who does.

 

[boltfluter]

Looks like there may have been a little metal build up on one of the flutes during chambering. I would think they could be polished out fairly easily. Can you feel anything on the cases with a finger nail?

Paul

 

[DaveTooley]

Looks exactly like chambering artifacts to me...

I'm not sure how I'd do that even if I wanted to.
Just out of curiosity lay a straight edge along the side of a fired case and see if the case body is straight.
You say this happened after annealing and not before?

 

[tobnpr]

That's downright ugly

Savage. Customer sent me the rifle brand new/unfired, to do some truing work on the receiver, bedding job and muzzle threading/brake. Discovered the chamber problem test-firing before sending it back.
Told him he should send it back to Savage for a replacement barrel, but between lack of faith in Savage and likely months for him to get it back he told me to fix it. Think I had to set it back two revolutions to clean up the chamber.

 

[Ggmac]

Thats the new threaded chamber , takes special threaded brass . Very hard to get here .

 

[AckleymanII]

1. Chambering issue from the start. This could probably be polished out.

2. bolt click is a issue between the dimensional differences between the die and the chamber.

3. Send fire formed brass to Harrells, he will make the proper die.

4. looks like the reamer was extracted with butt load of chips on it while the chuck was turning, Cut was too deep on one pass, not enough lube. NON pre bored chambers produce some ugly large chips.

5. my best guess

 

[Lefty Trigger]

I "painted" a piece of fired brass with a sharpie and the only drag marks are at those rings. The guy that made my barrel is going to send me a chamber hone on his dime to try or he said I could send it back, I chose not to send it back. He also said it was most likely chips that marked it.
For some of the other replys above,.. I have NO bolt click on opening. It opens just fine but will not just slide back, you have to give it a little nudge with your palm.

 

[gunsandgunsmithing]

I "painted" a piece of fired brass with a sharpie and the only drag marks are at those rings. The guy that made my barrel is going to send me a chamber hone on his dime to try or he said I could send it back, I chose not to send it back. He also said it was most likely chips that marked it.
For some of the other replys above,.. I have NO bolt click on opening. It opens just fine but will not just slide back, you have to give it a little nudge with your palm.

Lacking primary extraction?

 

[Lefty Trigger]

Lacking primary extraction?

Do you mean when the bolt opens and cams to the rear? It does that ok but just requires a little more tug to free the brass.

 

[gunsandgunsmithing]

Do you mean when the bolt opens and cams to the rear? It does that ok but just requires a little more tug to free the brass.

Yes. Primary extraction is what breaks the tapered case away from the tapered chamber walls. It doesn't take much but there should be enough that there is no resistance to pull the bolt back once it is completely unlocked from the lugs and extraction cam.

 

[DaveTooley]

One of the catch 22's of chambers. With minimal end gap between the bolt and the barrel there is a portion of the case that the FL die can't size. Over time even this thicker case section will expand causing what you described. Primary extraction is supposed to move the case just enough to overcome this. Sometimes it does and sometimes it doesn't. But then that's where the click comes into play.

 

[Lefty Trigger]

One of the catch 22's of chambers. With minimal end gap between the bolt and the barrel there is a portion of the case that the FL die can't size. Over time even this thicker case section will expand causing what you described. Primary extraction is supposed to move the case just enough to overcome this. Sometimes it does and sometimes it doesn't. But then that's where the click comes into play.

Yeah I have been thinking long on this whole weird issue. I think before I do anything to that chamber I'm going to try some new brass and see if it "sticks" in there. The brass I'm using does have quite a few reloads on it so it seems simple to give it a try before I go janking around with chamber demensions and power tools.