What would cause this?

[Bemachinist]

Posting for a friend. He sent me pics of some cases bulged out that came from this gun. Alexander Arms upper 16 lightweight barrel I believe. Factory Hornady 123 SSTs. 11 out of 200 rounds had this form. Extracting too early? Gas system not tuned?

Thanks.


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[LRRPF52]

Pics too small to see, but looks like normal brass to me.

You typically have a noticeable difference in appearance down there around the case web.

As long as there is not an actual dimensional bulge like we've seen with the PPU, it appears to be normal.

[Bemachinist]

Maybe this this one is bigger. So you think it's normal? Mine don't bulge out nearly this much. I've only shot about 500 rounds of 6.5G in my experience. But it seems a little out the ordinary.



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[StoneHendge]

Can you feel it with your fingernail on the outside? I've gotten that with both factory ammo (123 Amax and Black) and bagged hornady brass through both my Stoner / Satern barrel as well as my JP. I've attributed it be being sh!tty Hornady brass. I have a pretty big lot from factory ammo that was close to 400 and is now down to 350. Culled out the ones that looked like that - most after the first firing and a few after the second. No culls after the third for the remaining 350, and none after the 70-80 or so that have been fired four times.

Edit Add: I've put 300 pieces of Lapua brass through my JP twice and about 100 of those through it a 3rd time and have seen nothing similiar

[LRRPF52]

Can you measure the two ODs between the web and the body? Looks like the body expanded into a chamber on the large end of the spectrum, but I can't tell it it's just the high polish showing something that is normally there.

[bj139]

That looks like it could be a mark from the reloading die. Is there a difference that can be measured with a caliper?

[Kilco]

Pictures don't really show if it's just a visual Mark on the case, or if that's a literal bulge.

[StoneHendge]

I pulled this one out of my recycling bin. It is once fired from factory ammo (don't know if it was amax or black) so it has never been through one of my dies. The straw represents the measurement to the inside bottom of the case. The line can be felt with my fingernail. The picture resolution limit really makes it hard to define the very slight rise. Measures .442" above the line; .439 below

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[LRRPF52]

I had the same questions many years ago. Here's how my polished, unsized brass looked:






I was concerned enough that I sectioned one sample after feeling around inside with a bent paperclip to see if there was a weak area at the web/body wall junction.




There was nothing, and that brass has been loaded many times since then, comes out looking almost new every time I fire it. Lapua brass.

[Lone Hunter]

My brass looks like that also. I wet tumbled it and looked and looked but could not find anything wrong with it. New to the Grendel but seems like a lot of brass looks like this. It looks like that with Federal,Hornady,and Lapua brass. My barrel is a 20" BHW Barrel and it shoots really good. Using Forster dies. Wondered if it was because of the shell holder or what but I used different ones and the same thing. It chambers fine so I will watch it but not going to worry about it too much.

[Bemachinist]

He sent me some measurements, .444 at the bulge area. .437 at the area between the bulge and extractor groove.

[Bemachinist]

Sounds like this phenomenon is fairly normal, just more pronounced than other cartridges. I've seen it just slightly on some .308 cases I've shot too.

[Klem]

Either your brass is soft or the diameter of the breech is on the large size (or both). Looks normal, or at least not dangerous. If you are looking on the inside for signs of impending case-separation (from too much headspace) it will be towards the middle of the case, not at the join of the web and the body. In this case the headspace looks fine but the chamber might be a bit sloppy. If the case survives the first firing then you only need to squeeze it back enough to be reliable. That will maximise your case life.