Tiny sharp edge around the case mouth after loading?

[Ted Bell]

Hello all. I experienced an issue that I have not run into before and wanted to get your thoughts on it. It's 6x47 Lapua, Lapua 6.5x47 brass, Berger 105 hybrids. I received the brass new and full length sized them down to 6mm, and they have been fired three times. It has hardly stretched at all so I have not had to trim it. I did not chamfer it. It has been fired and reloaded three times with no issues. I wet tumble with stainless steel to clean and full length resize each time for .002 neck tension. However, on this fourth time, there seems to be a sharp edge around the perimeter of the case mouth on a lot of the rounds after the bullet has been seated. I can measure it at about .002 compared to a loaded cartridge without the lip, and it prevents those rounds from chambering. I'm puzzled as to what would have caused it this time but not previously. (The difference in length between these 4x loaded rounds and still loaded 3x loaded rounds I have is less than .001, FWIW.) I carefully filed down this lip and could then chamber the round - I'm not looking forward to doing that on the 40 rounds that have this issue.

Thanks,
Ted

 

[Precision Underground]

How big is it? How far down the neck I mean.

 

[317millhand]

neck tension is possibly too tight causing the mouth to flare a small bit when seating a bullet. are you using the expander plug in your sizing die?

 

[Rocketvapor]

It might seem anal but I take a piece of 400 to 600 grit paper, hold it in my palm and hit the end of the neck so I see flat shiney brass. Nicks and sharp edges tend to crack initiation sites.

 

[MtnCreek]

Burr created by the SS pins? Lightly cut inside and outside of necks every firing.

 

[Ted Bell]

it's just a sharp edge right at the edge and all the way around the rim- it can't be seen but I can feel it with my fingers. It's almost like I held the case upsidedown over a piece of sandpaper and sanded the case down a little bit, creating an edge all the way around. Chamfering would definitely fix it, but I don't understand why it suddenly appeared, and not on all the brass, but a decent number. I'm using the expander plug, and have not changed any of my settings on my dies or any of my reloading steps.

Thanks,
Ted

 

[Codiekfx400]

I would bet that the ss pins are creating the issue.

 

[Ted Bell]

I would bet that the ss pins are creating the issue.

It was ss chips, but now that I think about it you might be right. Because of an issue with my tumbler I ended up tumbling them longer than I usually do.

Thanks,
Ted

 

[Praeger]

It was ss chips, but now that I think about it you might be right. Because of an issue with my tumbler I ended up tumbling them longer than I usually do.

Thanks,
Ted

Tumbling with SS chips would seem unlikely to result in such a uniform edge on the case mouth. If anything, it would be the opposite - rounding edges. Have you disassembled and inspected your sizing die for any debris or burrs?

 

[Crawler]

I just ran into this myself the other day on Lapua 6CM brass. I’m using Redding dies. I don’t normally use the ss pins when I tumble them. But for whatever reasons I did. I pulled all the loaded rnds, made sure the decaping pin was out and ran them through the sizer die and de-burred them, also touched them up with my VLD chamfer. I pulled the sizer and seating does apart and gave them a good cleaning. Honestly didn’t find issues. So like others said probably the SS pins

 

[Wheres-Waldo]

Does tumbling with chips produce the same case mouth peening that pins does?

 

[CK1.0]

This is a product of wet tumbling, whether using SS pins, chips, or nothing but water.

The cases bounce around in the tumbler and the case mouths crash into other cases over and over again, messing them up and peening them. Usually, the chamfer/deburr process isn't enough to get rid of it and they usually need to be trimmed in order to fix the cases.

I tried just about everything while trying to find a way to wet tumble without the case mouths peening to no avail. I stopped wet tumbling my precision rifle cases and switched to using a vibratory tumbler and dry media and it stopped happening.

Now I only wet-tumble blaster ammo.