Gunsmithing Chamber issue caused while shooting today (pic)

[408w]

Quick run down

- Out shooting today, shot several rounds, then rounds would no longer chamber/bolt would not close. So I stopped and went home. This is a 300 win mag.

- Tried again at home no luck. Tried a Hornady modified case and it would not let the bolt close either.

- cleaned the chamber and now the rounds will go in and bolt will close but have groove marks on the brass and bullet. Thoughts or advice. Getting a bore scope to get a better look this week.

 

[408w]

None of the brass shot before the ammo quit chambering have marks like this on them.

 

[blairmckenzie1]

what kind of rifle? what do the primers on the rounds that you shot earlier in the day look like?

 

[408w]

They look fine/ normal. Thinking a small piece of debris of some sort got in there possibly not letting the rounds seat all the way into the chamber. Not sure about the scratches. Ruger precision rifle.

 

[blairmckenzie1]

Everything tight? barrel nut, handguard ect

 

[408w]

Have not checked the nut hand guard is. Rounds chamber now after the cleaning so I don’t think it is going to be loose/ head space issue, but I will check it out.

 

[supercorndogs]

Are sure those aren't marks from the feed ramp or contacting the mag as it was fed into the chamber.

 

[Steel head]

Are sure those aren't marks from the feed ramp or contacting the mag as it was fed into the chamber.

That’s what they look like.

 

[Terry Cross]

Factory or custom barrel?
Can you take a pic of the bolt counterbore ( if it has one ) and the edge of your chamber?

I would guess the rounds are having to clear a sharp edge on the way in.
That could take brass and/or copper shavings into the chamber. Only takes a tiny piece at the shoulder of the chamber to keep the bolt from closing easily.


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[sandwarrior]

Quick run down

- Out shooting today, shot several rounds, then rounds would no longer chamber/bolt would not close. So I stopped and went home. This is a 300 win mag.
View attachment 7291516

- Tried again at home no luck. Tried a Hornady modified case and it would not let the bolt close either.

- cleaned the chamber and now the rounds will go in and bolt will close but have groove marks on the brass and bullet. Thoughts or advice. Getting a bore scope to get a better look this week.

As noted a piece of debris, possibly a shaving from the case/bullet, that rolled as you inserted the case into the chamber. I wondered why they looked so uniform.

I'll agree as well to looking for a sharp edge that took that little piece off.

The other thing I would look for is if you didn't chamfer your brass and it picked up a small sliver of copper that sits in the bullet neck junction until knocked free.

 

[408w]

Those marks are from a round that I carefully slide into the chamber by finger then slide the bolt forward and closed it.

 

[supercorndogs]

Did you hold the round to keep it from dragging down the inside of the action on the way out? I.E. Is that where the bullet and brass dragged on the front end of the ejection port? It would take something pretty hard to gouge the chamber like that. The marks are also on a part of the bullet that doesn't touch anything when sitting in the chamber.

 

[Unknown]

Bore scope is a great idea.. Those look like chatter marks while the round is feeding forward...almost as if the round was scratching over something sharp as they are all in a line.

I would first check portion of the magazine where the rounds pass over before entering the chamber and look for any burrs or sharp edges and smooth them off. Then check any area where the rounds pass over on their way into the chamber. If you do find a sharp edge that the rounds are scraping against, as stated in previous postings, it doesn't take much of a shaving to keep things from chambering. I would also carefully check the recess where the ring around the cartridges base headspaces to see of the little piece of debris got deposited there. Some kind of debris either near the shoulder or the headspace ring could cause the problem.

 

[Wannashootit]

My take as well, is it's related to feeding.
I can't think of any circumstance related to the chamber itself that could engrave a boolit ahead of the bearing surface. It never touches the chamber walls- or the rifling. A serious burr ahead of the neck, maybe- but the same engraving at the shoulder precludes that.

Sure looks like it's dragging over a sharp edge or burr. If you look closely, the pattern is not consistent- the "skip marks" are much closer towards the end of the bullet.