Is this dangerous?

[HockeyDad]

Sumpin just hit me. Could my RCBS die be leaving me with a concentricity issue? It's the first time I've used the .300 WM one.
Am I going to have to buy a concentricity guage too?
Man, this is getting expensive, LOL !

 

[Phil Rizzo]

It is possible.
When you roll a loaded cartridge across a glass table, make sure it doesn't bump/hop.
Some guys rotate the case 180* and cycle the press again, after seating.
To minimize run-out.

 

[fseaman.js]

die be leaving me with a concentricity issue?

If it's the die, RCBS will replace it. No questions asked in the old days.

If the 180° twist trick works it may not be the die but the setup. Lots of things to try like flipping the locking ring over. This is why the floating die in Co-Ax presses is popular. Tuning/tramming your press is a thing, just like a lathe or mill. ;)

 

[fseaman.js]

Am I going to have to buy a concentricity guage too?

That's part of the fun, isn't it?

I bought all the toys. Multiple versions of concentricity gauges. Each has their plus and minus. A Hornady plus is it lets you "fix" a minus is "fixing" can mess up tipped bullets.

 

[FEENIX]

If the 180° twist trick works it may not be the die but the setup. ;)

... or an issue in part of the reloading process. Sadly, often, we forget or refuse to reevaluate our processes simply because we have been doing them for X years. There were a couple of threads this month, in which the OP claimed that he has been reloading for 50 years but never heard or used a comparator - you participated in that discussion. LOL!

The other claimed X years and was very sure that his process was sound, but he did not provide specific information in his effort to protect a brand name for us to help him troubleshoot. When I provided an example of pertinent information that was beneficial, he asked what my process was to keep my ES and SD low. I am no expert or claim to be, but as a continuous learner, I have learned to troubleshoot my issues, avoid them in the future/adjust my processes accordingly. A borescope might lead to another assumed or perceived problem that might not even exist if the end user does not know what they are looking for.

 

[DUCKMAN11]

Take a fired case and a pair of needle nose pliers. Lightly crimp a bullet into the fired case at your seating depth. Chamber the dummy and see if the bullet gets pulled out of the case by the rifling when you unload.

You're either dealing with an improperly short throated 300wm which is highly unlikely beings you have 100 rounds of factory ammo down the tube...or you have a burr in the chamber or something is scratching the bullet during the feeding process.

 

[terry 338rum]

that is not rifling you have another problem and i do not know what it is.

 

[Rflshootr]

After all of this discussion, I'm still betting there is a built-up carbon ring in the chamber. The 1st thing I'd do is give it a good scrubbing with some bore cleaner and a new bronze brush, then see if there is still a problem.

 

[Dean2]

After all of this discussion, I'm still betting there is a built-up carbon ring in the chamber. The 1st thing I'd do is give it a good scrubbing with some bore cleaner and a new bronze brush, then see if there is still a problem.

Yes, the old adage continues to apply. Start with the simplest, cheapest issues and work up the ladder. A few structured tests, measurements and a 50 dollar bore scope would quickly isolated the issue(s).

 

[HockeyDad]

After all of this discussion, I'm still betting there is a built-up carbon ring in the chamber. The 1st thing I'd do is give it a good scrubbing with some bore cleaner and a new bronze brush, then see if there is still a problem.

Sorry this reminds me of a joke.
In the local Catholic hospital, young Murphy is diagnosed with hemmoroids. The treatment: brush the area with a horsehair brush. O'Reilly is diagnosed with gonnorhea. The treatment: Brush the area with a horsehair brush. Seamus McMurtry is diagnosed with infected gums. The tratment: Brush the area with a horsehair brush.
One day the priest comes through the ward. He asks if anyone has any wishes.
McMurtry jumps up and say, just one day, I'd like to be first in line for the horsehair brush.

 

[Rivergrant]

I've had those marks in the past when checking rounds or after a walk in the woods. I found that pressing on the cartridge (against the direction the ejector is pushing) as soon as the cartridge was visible resulted in no marring/scraping. As others have pointed out, you have some light scraping on the shoulder/wall junction and more scraping on the case mouth and bullet. All of that scraping occurs on the same line of the cartridge.
Have you chambered and extracted a factory round that doesn't exhibit the same markings? Because it should, if it's an extraction deal...like it was for me.
Good luck!