Why am I splitting necks?

[CatShooter]

A couple of thoughts;

3. Post #28 .002 bump which is good but would not account for earlier head separation. Did you change your sizing?

4. I once neck sized a 260 for a while and then switched to fls...the worst case of donuts result. The expander pulled real hard out (like you mentioned). The bullets seated deep pushed the donut back out. My best guess was the donut material was "nicked" (for lack of a better word) during chambering/firing. The damaged (thin)spot at the neck/shoulder junction now became the weak link and was stretched thinner at each successive firing.
Neck splits as yours began shortly after. They could be spotted prior to splitting as a small imperfection. Often a small split wasn't spotted until the brass was loaded.
Cure was start over with new brass (rem) from same lot. FLS only with .002 bump. Check and ream donuts after every firing (usually only twice and they didn't show up anymore). Got up to 35 loadings from that lot but usually the pockets were gone by 20. One more thing I don't anneal until bullet seating becomes erratic.
My nickels worth,
Randy

The case head separation I had was with a .002 bump with Hornady brass. I thought I must have been over sizing too, but it doesn't make sense it would separate with a .002 bump. I'm not seeing any donuts, but I'll take a real good look again later on.

I question / thought for both of you gentlemen.

1 - Why are you "Bumping" 0.002"?? What problem are you trying to solve. Why not neck size and live a happy life?
2 - From what point are you using to measure the 0.002"
3 - IF you started FL sizing, and got head separations, isn't that telling you something?
4 - You cannot get "donuts" from sizing, unless the shoulder is flowing into the neck - and that means you are over sizing your cases by a LOT.

Reason I ask, is... I currently load for 31 rifles, and I have been loading since 1952 (I was 12), and I shoot a LOT... I have never had a head separation or a split neck from a case that was not already split in the bag.
I also NEVER FL size, unless it is to get cases from a different chamber to fit the current rifle.

 

[Creedmoor shooter]

I question / thought for both of you gentlemen.

1 - Why are you "Bumping" 0.002"?? What problem are you trying to solve. Why not neck size and live a happy life?
2 - From what point are you using to measure the 0.002"
3 - IF you started FL sizing, and got head separations, isn't that telling you something?
4 - You cannot get "donuts" from sizing, unless the shoulder is flowing into the neck - and that means you are over sizing your cases by a LOT.

Reason I ask, is... I currently load for 31 rifles, and I have been loading since 1952 (I was 12), and I shoot a LOT... I have never had a head separation or a split neck from a case that was not already split in the bag.
I also NEVER FL size, unless it is to get cases from a different chamber to fit the current rifle.

I FL size because I dont like to have to FL size every few firings anyway because it gets too stiff to chamber. That completely defeats my purpose of doing the same thing every single time. There's no stiff chambering, it just slides in no problem. I'm measuring the .002 off the shoulder with a gauge. I used to neck size. I started doing tests to see if there was any difference in neck sizing or shoulder bumping as far as accuracy goes. I found it didnt make any difference so I just went to bumping shoulders. Just a personal preference is all. I think once I get my bushing die set up the issue will go away. Like I said I didnt have neck split issues with the thinner hornady brass, I think the thicker stuff is just getting over worked in my particular die. The case head separation however has me alittle puzzled.

 

[CatShooter]

I FL size because I don't like to have to FL size every few firings anyway because it gets too stiff to chamber. That completely defeats my purpose of doing the same thing every single time. There's no stiff chambering, it just slides in no problem. I'm measuring the .002 off the shoulder with a gauge. I used to neck size. I started doing tests to see if there was any difference in neck sizing or shoulder bumping as far as accuracy goes. I found it didn't make any difference so I just went to bumping shoulders. Just a personal preference is all. I think once I get my bushing die set up the issue will go away. Like I said I didn't have neck split issues with the thinner Hornady brass, I think the thicker stuff is just getting over worked in my particular die. The case head separation however has me a little puzzled.

You can only "bump" a shoulder in a true bump die (as made by Forester).

When you FL a case, the first thing that happens is the body gets sized down (which is never necessary). When the body is squished, the shoulder and neck are pushed forward - the case gets longer.
Then, at the end of the ram stroke, the now longer case hits the shoulder of the die and the case shoulder gets pushed back - which means the excess case length is forced up into the neck, and your case is on the way to ruination.

For cases to last, there should be some resistance in closing the bolt handle - it means that the case is being held firmly against the chamber shoulder.
If there is any space at all ("There's no stiff chambering, it just slides in no problem."), then that space will turn into case stretch when the case is fired - when you add 0.002" to the next sizing, that becomes more case stretch on the next firing.

 

[MNbogboy]

You can only "bump" a shoulder in a true bump die (as made by Forester).

When you FL a case, the first thing that happens is the body gets sized down (which is never necessary). When the body is squished, the shoulder and neck are pushed forward - the case gets longer.
Then, at the end of the ram stroke, the now longer case hits the shoulder of the die and the case shoulder gets pushed back - which means the excess case length is forced up into the neck, and your case is on the way to ruination.

For cases to last, there should be some resistance in closing the bolt handle - it means that the case is being held firmly against the chamber shoulder.
If there is any space at all ("There's no stiff chambering, it just slides in no problem."), then that space will turn into case stretch when the case is fired - when you add 0.002" to the next sizing, that becomes more case stretch on the next firing.

 

[MNbogboy]

I've had great shooting neck sized only ammo.
Problem for me is that tight fitting ammo exposed to dusty hunting environments like Wyoming can be a problem when it becomes difficult to open or close the bolt.
Second reason for me is that I usually chamber two barrels at a time and try to work up common loads for for both barrels (sometimes not). Head spacing for two barrels is another task and can usually be done to a half a thou. But then they still end up a tad different. I usually try to size to .001-.0015. But .002 I believe is still good and not bad. Better than not being able to close your bolt up in the high desert.
Those are my reasons,
Randy