What's the earliest you've developed a carbon ring?

[CStroud]

I have a 300 Norma that I had chambered by a very well respected smith. The rifle has approximately 25 rounds of factory Norma ammo loaded with 230 gr bergers. Late last deer season I shot a nice 8 point late one evening and left a loaded round in my chamber when I put my rifle back in the safe...dumb I know. I remember the bolt lift was VERY stiff so I took a pic of the brass (included below). A few days later I went to eject the round and the bullet stuck in the chamber while the casing ejected and flung gun powder across the garage. I tapped the bullet out very lightly (pic below) and the bullet had what looked like some corrosion on it. I did not own a borescope at the time so I cleaned my rifle well and put it away for the summer. A few days ago I remembered this whole debacle while I was putting something away in the safe so I grabbed my Norma, put a round in it, and the bolt felt hard to close. Could all of this be from a carbon ring, or are my problems a bit more serious? I have ordered a Teslong bore scope and it should be here in a few days, just thought I would start this thread and see if I may have something more serious on my hands.

ETA: got the borescope in and checked things out. Not as bad as I expected at all, and got it mostly clean. I’ll see how it shoots in a week or so.

 

[KnowNothing256]

My first thought would be corrosion, rather than a hard carbon ring causing your problems. Either way, you're going to have to clean it all out, carbon and rust and copper.

Be prepared to see pits in the bore with your borescope; having blue on the bullet that was in the bore is a pretty sure bet you've pitted it. How badly, and how much it affects accuracy, is a toss-up.

 

[Aftermath]

That looks like galvanic corrosion. The dissimilar metals were reacting with each other. It's a real common thing and well documented but I've not seen it in a rifle before, probably because leaving a round chambered isn't something most folks do. Not knocking you. Shit happened.

EDIT for this link:

Galvanic Corrosion Explained

Contact between dissimilar metals – like copper fittings threaded into steel pipe or copper flashing fastened with steel nails – sets up an electro-chemical reaction that causes corrosion and leads to failure of the “less noble” metal

www.protradecraft.com

 

[CStroud]

Yeh I had kinda thought about the galvanic corrosion as well. Oh well, I’ll see what the bore scope shows when it comes in.

 

[TheJeanyus]

I had a 6.5 Creedmoor barrel develop a carbon ring in the first 35 rounds. The chamber was cut out of spec (too long) though.

 

[brianf]

Unless it’s an issue like a bad chamber

cleaning your rifle after each range session…
then there is no such thing as carbon ring.

Just find Bartlein posts , he’s posted is 2000 times.