What caused this

[old codger]

Purchased some once fired 300 Savage cases at a gun show. The cases have been sized, de-primed and cleaned. Whatever cleaning method they used is perfect. Cases are absolutely spotless, including the primer pockets and the case interior. My problem is a raised ridge at the mouth of the case both in the inside and outside of the case mouth. I am guessing that whatever cleaning method they used caused this. It seems the case mouth had been peened. See the sketch.

 

[cavedweller60]

I've seen cheap bulk processors use cement mixers to clean large amounts of brass. If the problem is on every case I wouldn't think that would do it but, if it was on some of them, I could see that causing the issue.

 

[Oso]

I see this type of bur from the use of a powered endmill cutter to trim case length. As the cutter dulls it stops cleanly shaving off the excess brass as it advance downward. Instead, the excess brass starts being smeared/relocated to the outside of the case mouth creating a lip/bur. Tumbling with Steel Pin usually knocks these burs off the cases. Lessons learned forming buckets of 300BO cases...

Educated guess is that they Wet Tumbled with steel pins (clean primer pockets) and then trimmed to length, which is why bur remained on case.

 

[drop_point]

I've seen this with cases cleaned in a wet tumbler and ran too long. Its from the tumbling media crashing into the case mouths.

 

[ricco1949]

Wet tumbling with pins. Brass fills with pins and become little ball peen hammers on each other.

Chamfering may or may not remove it depending on its severity. I've seen it go .025+ up the neck and need turning to remove.

 

[Doom]

If the cases are of uniform length it may be deformation of the brass from a cutting head on a trimmer. This would likely show up as a flat spot on the end of the case. Happens with softer necks and usually when large amounts of brass is trimmed. Otherwise its likely tumbled with pins.

 

[Straightshooter1]

Purchased some once fired 300 Savage cases at a gun show. The cases have been sized, de-primed and cleaned. Whatever cleaning method they used is perfect. Cases are absolutely spotless, including the primer pockets and the case interior. My problem is a raised ridge at the mouth of the case both in the inside and outside of the case mouth. I am guessing that whatever cleaning method they used caused this. It seems the case mouth had been peened. See the sketch.View attachment 1643745View attachment 1643745

It's common that trimming cases to length leaves burrs on both the inside and outside the mouth of the case. I often see virgin brass in this condition. This is why after trimming chamfering the inside and deburring the outside needs to be done.

As far as web tumbling with pins, which can get the brass really nice and clean as you've described, it tends to peen the mouth where the edge of the mouth is rolled inward and seldom results in rolled burr on the outside. So, I'd say it's not from the cleaning process, but just the typical result of the trimming process that brass has gone through.

 

[Webster]

Purchased some once fired 300 Savage cases at a gun show. The cases have been sized, de-primed and cleaned. Whatever cleaning method they used is perfect. Cases are absolutely spotless, including the primer pockets and the case interior. My problem is a raised ridge at the mouth of the case both in the inside and outside of the case mouth. I am guessing that whatever cleaning method they used caused this. It seems the case mouth had been peened. See the sketch.View attachment 1643745View attachment 1643745

Would trimming to the recommended case length get rid of it?

 

[Walt Krafft]

Wet tumbling with pins has done that to me. Nice and clean but burrs on both inside and outside of the mouth.

 

[6.5 forever]

Chamfer and debur. Easy fix.

 

[old codger]

With 300 Savage and such a short neck I don't want to trim them, they are at or slightly below minimum length.