Case Head Separation

just_jon

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I was doing some load development this morning with my T/C Encore 22-250AI and had my first case separation in over 35 years of reloading. Brass was twice fired Lapua 22-250 Rem. Load was 40.0 grains of a Varget which Nosler lists as their max load for a 52 grain bullet. I worked up to this load starting at 37.0 grains and saw no pressure signs. Speed was 3,983 from a 26” barrel. Brass was annealed and full length resized with .002 shoulder setback. I checked the remaining brass with a paper clip and felt nothing inside the case that would indicate this is anything other than an isolated instance. Interested in your thoughts.
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rammac

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That's not a head separation, that's a case fracture due to overpressure from too hot of a load. The pressure built up to the point of case failure before the brass had time to obturate (expand in to the chamber wall).

Nosler #6 manual lists 36 grains as the max for their 52gr Custom Competition bullet.
Hornady 10th edition manual lists max as 35.7gr.
Berger 1st edition manual lists max as 36gr.

I think that you've found out that visual indicators of high pressure are pretty unreliable. A tight chamber and zero headspace isn't going to reveal much in the way of brass or primer deformation because there isn't any place for the cartridge case metal to move. If three major brand manuals all say that 36 grains is the max then I'd bet that 40 grains is well over max.
 

cohunt

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That's not a head separation, that's a case fracture due to overpressure from too hot of a load. The pressure built up to the point of case failure before the brass had time to obturate (expand in to the chamber wall).

Nosler #6 manual lists 36 grains as the max for their 52gr Custom Competition bullet.
Hornady 10th edition manual lists max as 35.7gr.
Berger 1st edition manual lists max as 36gr.

I think that you've found out that visual indicators of high pressure are pretty unreliable. A tight chamber and zero headspace isn't going to reveal much in the way of brass or primer deformation because there isn't any place for the cartridge case metal to move. If three major brand manuals all say that 36 grains is the max then I'd bet that 40 grains is well over max.
are you looking at the 22-250 or the 22-250 AI data? OP has the 22-250 AI
 

just_jon

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I’m using 22-250AI data direct from Nosler’s web site. Data is the same in their #4 guide (attached). I suspected it may have been a fire forming issue, but I seated bullets into the lands per Nosler’s recommendation to prevent stretching in the web area (attached). I’m not seeing any case stretching in this 2nd firing (aside from the obvious) as all are still right at or just below the trim to length of 1.900”. Should I toss this brass and start over?
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BoomFlop

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You are also using a hollow point bullet of some kind and not a ballistic tip. This may seem minor, but could have a large difference between being fine and way over pressure.

Also, you are seeing 80 fps over their data which is also proof that you are over pressure. Nosler tends to be high on velocity for what you will actually see, and you are actually exceeding their velocity.

Not saying it is the cause, just be careful.

Steve
 

North Idaho Hunter

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Do you happen to have some virgin 22-250 brass?

IF so, measure base to datum on the virgin 22-250 brass, record -----> then measure base to datum on the formed 22-250 ai brass. compare the two, how much does the case stretch on that first firing?

I'm with @Farmerboy78 on this one - I'm betting your getting significant case growth on that first firing.

the only way I've personally found a cure around this if your getting significant case stretch on firing is by creating a false shoulder - sometimes jamming in the lands doesn't provide sufficient resistance to prevent excessive stretch at the web.
 

just_jon

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Good catch Steve. Thanks all for your input.

First time trying Varget in this chambering. Sucks because the 40 grain load put four shots, including the ruptured case, inside .4” at 100 yards with ES of 8 and SD of 3. Also sucks because it took a like of time and components to get to this point, but safety is paramount. Amazed that the shell that burst was #195 of 200 on their 2nd firing. Brass is in the trash and two boxes of Lapua on the way
 

just_jon

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I would start over, expand new brass to 6mm or larger and then run through a die that 0.003"ish Longer. To create a tighter fit for the chamber and be sure the shoulder is supported.
I think you are on to something. I’ve noticed more than the usual amount of soot on the case neck. How do you go about making the siz8ngbfue longer?


Do you happen to have some virgin 22-250 brass?

IF so, measure base to datum on the virgin 22-250 brass, record -----> then measure base to datum on the formed 22-250 ai brass. compare the two, how much does the case stretch on that first firing?

I'm with @Farmerboy78 on this one - I'm betting your getting significant case growth on that first firing.

the only way I've personally found a cure around this if your getting significant case stretch on firing is by creating a false shoulder - sometimes jamming in the lands doesn't provide sufficient resistance to prevent excessive stretch at the web.
Good point. I need to do a better job overall in recording baseline data. I will check case stretch when my new 22-260 get here.
 

Memberberries

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Would a full tilt fireform load cause the brass to stretch all in the one spot when converting to AI? Maybe try fireforming with a cooler load then turn it up.
 

rammac

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are you looking at the 22-250 or the 22-250 AI data? OP has the 22-250 AI
Yup, you're right, I missed the AI load info. My mistake.

I don't think that this is a head separation. With the powder marks down the case it looks to me like hot gasses were able to move along the case which means that the case didn't have time to expand before the bullet was out of the case.
 

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