Thread: Tight chamber and marks on projectile

Mystery solved, sort of. The borescope took a while to arrive, but now my question is wft is that? Looks like some kind of burr, but I can't remember how the heck did that happen!

Btw carbon didnt look too bad. But I can see a bit

Mystery solved sort of indeed.
I really don't see anything there that would cause hard bolt closing or the marks on the projectiles or the poor accuracy in a different rifle. The search is likely to continue. To me the problem is with the cartridge and not the rifle. To rule the rifle out a good look at the front of the chamber where the case neck ends and the throat starts would be useful to rule out a carbon ring at this point. Are you trimming your cases? If not they may be too long for the chamber, worth checking. My money is still on the loads being too long for the rifles chamber possibly complicated by the cases not being trimmed.
Regards Grandpamac.

Is that not a carbon ring?

Greetings @Kelton and all,
Looking at the pictures again (and not having a bore scope) I had miss read them thinking the ring was rifling or whatever. I think that you are right. This does not explain the rifling marks on the projectiles however so there may be two things at play, maybe three if the cases are over spec for length.
This is a learning curve for me as well so a bore scope may have just elbowed its way onto the list of things to get. Even an old dog can learn a new trick now and then.
Regards Grandpamac.

I’m by no means an expert but everything your experiencing I have had with my saum more shoulder bump and a hell of a clean solved it I had a borescope put down it by more experienced eyes than mine and it looked just like that was a carbon ring I now solvent clean the rifle more regular and issues haven’t come back luckily for me the barrel likes being spotless

Originally Posted by grandpamac

Greetings @Kelton and all,
Looking at the pictures again (and not having a bore scope) I had miss read them thinking the ring was rifling or whatever. I think that you are right. This does not explain the rifling marks on the projectiles however so there may be two things at play, maybe three if the cases are over spec for length.
This is a learning curve for me as well so a bore scope may have just elbowed its way onto the list of things to get. Even an old dog can learn a new trick now and then.
Regards Grandpamac.

I was also getting marks like that on my projectiles and I instantly thought rifling but lots of checks made and no change in seating depth had me scratching my head it was scratching on the ring I chased my tail for a bit changed nothing apart from removing the ring and everything came right again . The only rifle iv dealt with a true carbon ring on easy maintenance has seen it become a past issue

It also wouldn’t shoot until the barrel warmed up and the ring expanded first 5 were average then it’d shoot .2s for the rest of the session blimen havoc those rings

Carbon ring for sure. Has built up enough that its reduced the freebore diameter. Needs a decent scrub with a nylon brush, bigger than bore diameter. If it’s really bad, it may require abrasive on a tight patch.

From memory General Motors top end cleaner or carb cleaner turns carbon rings to jelly

I Havnt googled it but it’s a distant memory

I used boretech carbon cleaner a foaming bore cleaner that was awesome clr and finished it off with jb bore past and now a regular patch of the boretech it’s flawless il never let it happen again theor bloody stubborn to remove

To me it looks like...
On the left side of the 'line' is the transition into the barrel (a bit further down would show the lands) on the right of the line is the chamber.
The line is the build up of carbon ahead of where the case finishes. It may be deep enough that now the projectiles get scratched, depending on their shape.

Originally Posted by johnd

To me it looks like...
On the left side of the 'line' is the transition into the barrel (a bit further down would show the lands) on the right of the line is the chamber.
The line is the build up of carbon ahead of where the case finishes. It may be deep enough that now the projectiles get scratched, depending on their shape.

Left side is chamber and right side is barrel.

Definitely a carbon ring there. CLR on a nylon brush spun in the drill on the end of a cleaning rod will sort it asap. Just remember to thoroughly clean the CLR out with meths or alcohol. Then oil straight after, then a final dry patch.
Dry the chamber and barrel of CLR before rechecking with the borescope to check progress and then clean out CLR with meths etc.

Ha! Oh yeah, my bad. Anywho that's ya carbon ring.
How you dissolve it/ remove it is up to you, read up on what chemicals work with your barrel steel.
And how they can react to the outer coatings as well.

Originally Posted by grandpamac

Mystery solved sort of indeed.
I really don't see anything there that would cause hard bolt closing or the marks on the projectiles or the poor accuracy in a different rifle. The search is likely to continue. To me the problem is with the cartridge and not the rifle. To rule the rifle out a good look at the front of the chamber where the case neck ends and the throat starts would be useful to rule out a carbon ring at this point. Are you trimming your cases? If not they may be too long for the chamber, worth checking. My money is still on the loads being too long for the rifles chamber possibly complicated by the cases not being trimmed.
Regards Grandpamac.

Now that the OP has a borescope the actual chambered case length can be viewed.
Take a fired empty case, chamber it and close the bolt. Then, from the muzzle insert the Borescope and run it along until meeting the chamber / throat junction. You will be able to see if the case sits hard against that 90 degree shoulder separating the chamber and throat or whether there is clearance between the case throat and the shoulder. If there is contact it's definitely time for case trimming.
Try several cases this way to check possible variability in case lengths as some may make contact and others may not.

My comment on Carbon Rings. Periodically I scrub them out too. Usually with KG12, a good abrasive for this. I know the rings can affect accuracy so I don't ignore them but over several rifles I don't believe I've ever noticed an obvious accuracy detriment even after the rings have been in place for some time. So, I don't know at what point it matters but my practise of cleaning them out once or twice per year seems OK to me. That would be around every 200 to 400 - 500 rounds approx.