6PPC cracked necks

C

Chris M

Guest
:confused:Hi
I have attached a pic of a case fired in my new 6PPC rifle, out of sixty cases fired, seven have developed cracks at the base of the necks, these cases are on their third firing from new. Chamber is .262 neck and cases are turned to .0085 thickness. Berger Column bullets and 29grains of N133.
Any ideas anyone?
Regards
Chris
 

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PPC Brass

What brand of brass? Are you using a bushing die for neck sizing? Are you neck sizing close to .260? Brass that is not annealed will split much easier than annealed brass.
 
Chris,

I've never seen this in 20 years of shooting the 6PPC - until last season when one of our (very experienced) shooters got exactly the same problem.

Could it be a batch of brass we have in the UK - where turnover is relatively low compared to the US?

Vince (UK)
 
6PPC Cracked cases

zimmden said:
What brand of brass? Are you using a bushing die for neck sizing? Are you neck sizing close to .260? Brass that is not annealed will split much easier than annealed brass.
Click to expand...

Yes, using a custom bushing die, .002" neck tension. Brass is Lapua in the Gold cardboard box. I'm going to turn some new cases and anneal them before firing.

Chris
 
VinceB said:
Chris,

I've never seen this in 20 years of shooting the 6PPC - until last season when one of our (very experienced) shooters got exactly the same problem.

Could it be a batch of brass we have in the UK - where turnover is relatively low compared to the US?

Vince (UK)
Click to expand...

Hi Vince
I was shooting at Bisley on Sunday and neither Phil Sammons nor Steve Newman had seen any thing like it before. Nor could they think of anything I was doing wrong.

Chris (UK)
 
If you section a numerous fired 6PPC made from a 220 Russian Case, you will see a distinct line where the metal flowed from the originol shape of the 220 case to the larger 6PPC neck/shoulder. Regardless of our efforts, it will always seem to form a spot right there that is thinner than the rest of the neck.

I cured a lot of this by fire forming, and then turning the necks. The two pictures show a case neck turned before fire forming, and on neck turned after.

This is a .269 neck. Think how then that spot is on a typical .262 neck.

Annealing might help, if the cases for some reason are a tad brittle out of the box.


http://benchrest.com/attachment.php?attachmentid=15746&stc=1&d=1421079496
 

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jackie schmidt said:
If you section a numerous fired 6PPC made from a 220 Russian Case, you will see a distinct line where the metal flowed from the originol shape of the 220 case to the larger 6PPC neck/shoulder. Regardless of our efforts, it will always seem to form a spot right there that is thinner than the rest of the neck.

I cured a lot of this by fire forming, and then turning the necks. The two pictures show a case neck turned before fire forming, and on neck turned after.

This is a .269 neck. Think how then that spot is on a typical .262 neck.

Annealing might help, if the cases for some reason are a tad brittle out of the box.


http://benchrest.com/attachment.php?attachmentid=15746&stc=1&d=1421079496
Click to expand...

Thanks Jackie, I think you've cracked it (Pardon the pun) this is exactly where they have cracked. I've annealed the remaining fired cases and another box of 100 cases bought at the same time.

Chris
 
rcheek said:
Maybe you turned the necks too far into the shoulder.
Click to expand...

I had a batch of 25 where I did exactly that. Couple of times the neck stayed in the chamber and I couldn't chamber the next round. Happened during a match. Fortunately the necks just dropped out. Lesson learned!
 
It looks like it must be related to turning but one other thing to check would be to make sure you didn't load up some bullets with large die rings. I'd mic over some loaded rounds just to make sure you've got some neck clearance.
 
Carson said:
It looks like it must be related to turning but one other thing to check would be to make sure you didn't load up some bullets with large die rings. I'd mic over some loaded rounds just to make sure you've got some neck clearance.
Click to expand...

Thanks for the input
 
Sizing Die Set-Up

Chris,
Just saw your thread and thought I would offer another very simple suggestion... MAKE SURE that your "custom die" isn't trapping the bushing and consequently sizing the neck all the way down to the shoulder junction. If it is, your necks will crack way sooner than they would if you simply put some kind of a shim in the top of the die to allow the bushing to "float" .010" or so. Unless your chamber is crooked or you're seating flat base bullets all the way down to the neck/shoulder junction (I wouldn't expect either to be the case in a full-fledged BR rifle), leaving that last .010" or so of your neck unsized won't hurt a damned thing; but may well save you some aggravation.
Good Luck!
 
Kent Harshman said:
Chris,
Just saw your thread and thought I would offer another very simple suggestion... MAKE SURE that your "custom die" isn't trapping the bushing and consequently sizing the neck all the way down to the shoulder junction. If it is, your necks will crack way sooner than they would if you simply put some kind of a shim in the top of the die to allow the bushing to "float" .010" or so. Unless your chamber is crooked or you're seating flat base bullets all the way down to the neck/shoulder junction (I wouldn't expect either to be the case in a full-fledged BR rifle), leaving that last .010" or so of your neck unsized won't hurt a damned thing; but may well save you some aggravation.
Good Luck!
Click to expand...

Thanks Kent
I think the sizing die is free to float a little, but I will strip it, clean and check again. Thanks for your input.
Chris
 
Kent Harshman said:
Chris,
Just saw your thread and thought I would offer another very simple suggestion... MAKE SURE that your "custom die" isn't trapping the bushing and consequently sizing the neck all the way down to the shoulder junction. If it is, your necks will crack way sooner than they would if you simply put some kind of a shim in the top of the die to allow the bushing to "float" .010" or so. Unless your chamber is crooked or you're seating flat base bullets all the way down to the neck/shoulder junction (I wouldn't expect either to be the case in a full-fledged BR rifle), leaving that last .010" or so of your neck unsized won't hurt a damned thing; but may well save you some aggravation.
Good Luck!
Click to expand...

Different thickness "O rings" work well.
 
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