What causes this?

[LRSickle]

These are brand new Honady 6mm brass I was fireforming to 6mm AI. I picked a safe load for N160 and 95gr Hornady SSTs off Vihtavori website. I shot a 10 shot string and only one survived. I didn't inspect my brass until after I shot my 10 shots because I have a right bolt/left port and I stayed at battery while I fed new rounds with my left hand. I didn't notice any difference in recoil or report. This gun is a proven hummer with Rem and Federal brass and I've never had any problems with any other brand I've run through it. I've tried to look up the cause of this particular problem but only found the common causes of casehead separation, split necks and shoulders. Any ideas?

 

[tbrice23]

I've fireformed hundreds of 6AI and 270 AI with warm loads and with COW, I've never experienced that.
Are these old cases that have never been annealed????
I really don't know exactly what happened. BUT please check your chamber for gas cutting in the place where the cases ruptured.

 

[FEENIX]

WOW, that's very interesting. Since they are brand new Hornady brass, have you consulted with their customer service/tech support about it yet? Also, have a reputable gunsmith check your rifle just to be safe.

Good luck and keep us posted.

Cheers!

Ed

 

[Lefty7mmstw]

there is a rather significant diameter change going from 6rem to 6remai... There is no doubt in my mind that the brass is too stiff just past the shoulder area and they are letting go... I'd anneal further down or blow out a brand you have had luck with.

My brother and I have blown out hornady 375 brass to 7mmstw, but any one with the shoulder pushed back a bit too far was toast. We didn't loose any to side failure, but the diameter growth from 375 to 7stw is a lower % if I'm not mistaken than you are doing. Hornady brass is rather stiff brass; good if you are looking for toughness and high cycle count. Not so good if you want to re-work it.

 

[TexSavage]

I'm no expert by any means, but I'll give you my experience with fire forming brass. I started out reloading 35 years ago by means of the 30 and 357 Herrett. Now these wildcats were formed from virgin 30-30 Winchester brass, run through the resizing die of each wildcat. Then they had to be fire formed. The brass moved quite a bit, especially the 357 Herrett. The process I followed was finding a very mild load listed in the reloading manual and reducing the minimum of that load by 10%. Not sure if you just loaded up the minimum listing of a load of went below that. If you didn't you might want to retry it and the comment about another brand that hasn't had these drastic effects is also a good point. I am just now using my first Hornady brass in 300 WSM, no fire forming but we shall see what happens. Good luck to you and I hope you find the culprit and posit back with your findings.

As a side note, I never had any loss of cases and I probably fire formed somewhere in the range of 500 case combined. I still have those cases today. I used Remington and Winchester brass then and did it all before really giving case annealing much interest. Maybe I was lucky.

Also knew a buddy who did the same thing I did except he put a spall piece of paper in to protect the powder and then sealed the case with Crisco. Then shot into a trash can in his shop. He had no issues but I was not quite that brave to try it.

 

[LRSickle]

I've fireformed hundreds of 6AI and 270 AI with warm loads and with COW, I've never experienced that.
Are these old cases that have never been annealed????
I really don't know exactly what happened. BUT please check your chamber for gas cutting in the place where the cases ruptured.

I usually use COW to fireform but I don't have any pistol powder and I live remotely on an island in the Gulf of Alaska. Any time I fly into Kodiak I gather all the reloading supplies I can get. I just had some N160 that I had no plans for so I used that instead.
They are new unfired brass that I bought a couple months ago.
I checked the chamber and I don't see any gas cutting. I also fired some other reloads I had and didn't see any impressions of pitting on them. I still have the reamer so if I need to set the chamber back I can.

 

[LRSickle]

WOW, that's very interesting. Since they are brand new Hornady brass, have you consulted with their customer service/tech support about it yet? Also, have a reputable gunsmith check your rifle just to be safe.

Good luck and keep us posted.

Cheers!

Ed

I haven't called Hornady yet. I'll call them today.

 

[LRSickle]

I call Hornady today (**** cheerful guys I might add), and he wondered if the firing pin knocked the case to the front of the chamber and I'm getting case stretch as it expands backwards to fill my chamber. My primers are flattened which is typical of a headspace/case stretch problem. I still wonder why I'm getting linear splits instead of radial separation.

 

[Edd]

You need to open up those cases and examine them. The brass is either too hard to stretch or it is too thin to stretch.

 

[tbrice23]

You need to open up those cases and examine them. The brass is either too hard to stretch or it is too thin to stretch.

I wonder if you mic the necks if you would find that the split is on the thin side.

 

[Pdvdh]

You need to open up those cases and examine them. The brass is either too hard to stretch or it is too thin to stretch.

Yup. What Edd said!

 

[LRSickle]

I wonder if you mic the necks if you would find that the split is on the thin side.

I just checked them and you were right. On the split side of every case they were .014 and on the opposite side they were .0155. Hmmmmm.

 

[Pdvdh]

Too brittle is the bigger problem. You could try to anneal them further down into the case body. But the safer approach is different parent brass, IMO.

 

[LRSickle]

Too brittle is the bigger problem. You could try to anneal them further down into the case body. But the safer approach is different parent brass, IMO.

I think you're right about them being too brittle. I have fifty more Hornady brass but they are the same lot number. I think I'll have my son down in Idaho look for some different brass for me.