Case separation

[Elwood]

I gave this case to Dave (6mmBR) so he could take some measurements for a 6mmAI, he said he noticed a small faint line just below the neck wall junction. On applying a little bit of pressure it cracked!.

 

The case is a Winchester and the caliber is 6mm Crusader. It has been full length sized 4 times and annealed twice.

 

I have checked the rest of the cases with a magnifying glass and they all appear to be ok.

 

Any suggestions as to why this has happened?

 

[The Gun Pimp]

Ian,

 

Yes, unusual - it's usually at the other end! Could the annealing be a factor? What neck clearance are you running?

 

Vince

[Elwood]

Ian,

 

Yes, unusual - it's usually at the other end! Could the annealing be a factor? What neck clearance are you running?

 

Vince

 

Neck clearance is tight Vince, 2.5 thou total. Pete walker has had the reamer and he informs me that it is a 272 neck and not a 273.5 as I was informed. I'm now going to take at least another 1 thou off the necks.

 

Dave (6MMBR) had a look inside the case with his bore scope and said there was a visible line all the way round.

[1967spud]

Ian any chance of taking some measurements of the case either side of the split for me please

 

thanks

[Vermincinerator]

Elwood i had the same on two of my Nosler 22-250 AI cases, not as pronounced but a faint radial mark all the way round about an 1/8" lower down the case then yours.

I scraped the inside of the case with a dental probe and could feel a groove forming.

I crushed one of the cases with a pair of pliers and it did indeed fracture at the mark.

 

Ian.

[Chris-NZ]

Separation happens when the case above the crack repeatedly expands to grip the chamber wall and the remaining lower case doesn't grip and is pushed back under firing onto the bolt face. It's probably a combination of excessive resizing -and- annealing.

 

That's my 2c guess anyway

 

 

Chris-NZ