Dent below case shoulder

[dukerugger25]

I just finished full length sizing a hundred 300 PRC Brass (Hornady) and noticed a "dent/divot" on one side just below the shoulder. It is in the same spot on about 70 of the 100 brass. Any ideas what could be causing this? I cut one open and there is no discernible marks on the ID of the case, so the dent is on the outside only. The dent did not appear on resized ADG brass done at the same time.

 

[lash]

Is it new and unused brass or once fired? I’ve seen that when I had something stuck in my chamber.

I suppose it could also be from something stuck in your sizing die. It only takes a small grain of something like powder, brass flake or excess lube to do that.

 

[spife7980]

Looks pretty sharp small and concentrated unlike a too much lube divot.

 

[lash]

Looks pretty sharp small and concentrated unlike a too much lube divot.

I agree. As mentioned, I once had a small brass burr stuck in my chamber that gave me almost the same dent.

 

[PinesAndProjectiles]

Are your shoulder datum measurements the same on the Hornady as the ADG? What about OAL?

Could it be that the Hornady brass is longer, and you're just starting to crush the body during FL sizing?

May be stretch, but you never know.

 

[MarinePMI]

If it's been fired (assuming so, since you mentioned FL sizing it), it's the dent from the ejector, smacking the case into the chamber wall as the neck clears the chamber neck upon extraction. It can also be caused when the case ejects, and smacks the receiver as it flips out of the ejection port.

 

[dukerugger25]

Thanks for all the replies. It's been fired 1x.

I do not see it on ADG 1x fired brass, which is why I'm thinking it is not due to the chamber.

I fired 10 adg and 10 Hornady (verified no divot before firing) this morning and none showed divots post firing either. Will clean then and then size again later today to see what happens. Will also clean my sizing die like crazy.

 

[dukerugger25]

Measuring headspace using a Hornady comparator (0.420), both are giving the same measurements. The Hornady brass is 0.005" longer overall length, only difference.

 

[mtnhunter22]

Had this same issue and it turned out to be some small piece of tumbling media in my dies. Interesting though that it’s not happening with ADG. Assuming because ADG is a thicker brass.

 

[dukerugger25]

Mystery solved...My depriming die had a piece of media in it. I used it on Hornady brass but not the ADG.

Thanks guys!

 

[dukerugger25]

Second root cause identified, brass was smacking the parallax knob of the scope during ejection. I’m running an NX8 and it sits lower than the previous scope I had on the rifle. I put an O-Ring around the knob and this protects the brass.

 

[Steel head]

I agree. As mentioned, I once had a small brass burr stuck in my chamber that gave me almost the same dent.

I had a funky piece of carbon stick in my chamber that made similar dents.