Brass Case Head Separation after 6 firings

[longbarrelxp]

I have used the false shoulder approach for years, even on standard cartridges if the gun has a couple thousandths over minimum headspace. I go .020" to .030" depending on the next size expander I have.
To check brass for thinning in front of the thickened head area, I use a piece of wire with the end cut with dykes (nippers) so I can gently scrape the inside wall and feel for a dip in the inisde wall.

 

[RidgeTop]

I use this wire to reach all the way in and 'feel' the area for stretch.

 

[Mike Matteson]

A picture is worth a 1000 words. I have or having to step up into more fireforming my cases. I use to neck size my cases and not fully size the necks. Which stop my case splits in my belted mag. Now with my 6mm/280AI I am setting up to fireform by putting the bullet into the lands with a reduce load and firing the cases. Trying to be sure the base is against the bolt face. I think I am on the right side of this. I am using 280AI cases to start with. Thinning the necks to .012" now. Then sizing them to 6mm, and not bumping the shoulders presently in the resizing the necks. I have 2 test fired case presently and going to check with a comparator for shoulder change compared to unfired case. Down the rabbit hole again. Got to love it.

 

[Mike Matteson]

I use this wire to reach all the way in and 'feel' the area for stretch.

That works.

 

[nksmfamjp]

That works.

It works, but you only will feel when you have an extreme condition. That is why I keep the RBCS tool. It tells me how much thinning and actual thickness.

I do believe a paper clip can keep you from blowing yourself up.

 

[Shane Lindsey]

I had a hard time reaching proper case length with Peterson 270 brass when forming to the 338 Sherman. Also gave up a few to cracking parallel to the case body. This was with a false shoulder at the lands.

Peterson 280ai brass was a good fit for this and I think gave less "stretch". They were the correct length before even forming. I tried to just jam hard without a false shoulder, but it would give light strikes so had to go back to the false shoulder.

Too bad that barrel sucked...

 

[chav0_12]

I just want to say that I love this forum for the conversations like this. I haven't been down the road of fireforming wildcats yet but plan to in the near future. I absolutely love discussions like this one. Thank you all for your experiences.

 

[Muddyboots]

Teslong great for brass case head separation visual check.

 

[dennisinaz]

I like to lube the bolt face, seat the bullets as long as i can and get the bolt closed. You can jam the bullet into the case a little. Probably .025" into lands. I've played with lining the case body but you can't use full power loads of you do it. Gotta find the happy spot. This works well for 300 H&H to Wby and 260 AI. Never made a Gibbs case

 

[Mike Matteson]

I just want to say that I love this forum for the conversations like this. I haven't been down the road of fireforming wildcats yet but plan to in the near future. I absolutely love discussions like this one. Thank you all for your experiences.

Keep reading. When you think you have seen everything, guess again. There is some very smart people here, and items with information is always coming. As one person said here. It's my morning fix.

 

[dblman]

View attachment 365419

Anybody use this setup to look for thinning brass near the case head?

I do and found my 300 Sherman brass all scrapped after 6 firings. I'm pretty careful about sizing after firing. I target 0.003" shoulder bump because at my normal 0.002", there was still a bit of tightness in the final bolt close. Win 70 action.

I actually think it came from forming. Now the brass showed the brass thinned about 0.01" radially. After forming, I tested and saw 0.002-0.003" of this thinning.

So, my thought is my forming process was bad. I used a false shoulder created with a 0.312 (8mm) expander. I wonder if this wasn't enough. Bullets were jammed 0.005". I was using Peterson brass.

Now all I can find is new Starline. I'm thinking COW method and use 0.338 expander to get this false shoulder more solid.

Other advice? Am I heading the right way? Anything better.

I too worked forever making brass for a wildcat. Was talking with someone at Hornady and he said, "Oh, we can make you a hydraulic form die!"
No more fire forming.
New die uses water as its pressure source and works perfectly. Primer the case, best to use fired primers, fill completely with water, insert plunger and hit sharply with a hammer. Presto, you have a perfectly formed new, non-fired case.

 

[Mike Matteson]

The one thing. I was developing the type of brass to use for my 6mm/280AI setup. I started with the AI configuration, but using either 25/06, 270 or 30/06 case to fireform. I discovered the 280AI case and it being a little longer to the shoulder. More powder can be put in place. If I was going to increase some of the other calibers and conform to AI chambering. I would go to a 280AI case to build from. The 280AI case is about .1" longer to the shoulder than other case in 25/06, 270, 7mm, and 30/06 cases.
Now I don't have any information on what that 6mm/280AI is going to due yet. I will post it as it comes. That probable a few months off now.

 

[Mike Matteson]

I too worked forever making brass for a wildcat. Was talking with someone at Hornady and he said, "Oh, we can make you a hydraulic form die!"
No more fire forming.
New die uses water as its pressure source and works perfectly. Primer the case, best to use fired primers, fill completely with water, insert plunger and hit sharply with a hammer. Presto, you have a perfectly formed new, non-fired case.

Interesting! Will have to look into this more. The only thing is getting the shoulder to move forward to fit your chamber. I can see if changing the shoulders. If you are necking down how would that work?

 

[Lefty G-gear]

View attachment 365419

Anybody use this setup to look for thinning brass near the case head?

I do and found my 300 Sherman brass all scrapped after 6 firings. I'm pretty careful about sizing after firing. I target 0.003" shoulder bump because at my normal 0.002", there was still a bit of tightness in the final bolt close. Win 70 action.

I actually think it came from forming. Now the brass showed the brass thinned about 0.01" radially. After forming, I tested and saw 0.002-0.003" of this thinning.

So, my thought is my forming process was bad. I used a false shoulder created with a 0.312 (8mm) expander. I wonder if this wasn't enough. Bullets were jammed 0.005". I was using Peterson brass.

Now all I can find is new Starline. I'm thinking COW method and use 0.338 expander to get this false shoulder more solid.

Other advice? Am I heading the right way? Anything better.

Case gages are available for standard cartridges, and there are headspace gages to check to see if your chamber is too long, or about right, or just right. - Is this a rare chambering? - Then you have to make DAM*N sure it is all right.
My Dad had a custom .338 WM, then later found the chamber too long. - Dangerously long!= Cases separate, and screw you and your rifle up = BAD DAY. - I caught it and nothing happened. The neck-sized rounds would not fit in a stock .338 WM. Too long! - Sold it to a gunsmith who fixed it.