Neck turn gone wrong. Help please.

[Field_2_Fork]

The rifle in question is a Panda 6PPC, .263 neck. New Lapua brass (12 years old, gold box if that matters), first pass with K&M cutter/carbide pilot, second and final cut with a Pumpkin. My aim is to cut to .0085".
I'll post a couple pictures showing the first failed attempt, then what I thought was the fix which ended up with a neck coming off today.

First I turned the case below, just kissing the shoulder is what I was aiming for. I attempted to bump the shoulder in a FL bushing die but the bushing created a small ridge when running into shoulder material. I then removed the bushing and tried again but the die created a small crease further down the shoulder, about the same place I could see a mark if I chambered the round. The bolt closure was snug but acceptable I thought. I loaded up 15 and at the range that snug had changed to very firm to close the bolt. Closer inspection revealed what looks to be two ridges, one from the bushing and one from the chamber. You can sort of see the peak created between the two ridges in this pic.

A fellow I shoot with, he's been at this much longer than me had a look and suggested I turn further down. It made sense to me, so I turned far enough to eliminate both 'cut marks' and the peak in between. This shows before and after. (The before in this picture doesn't show the ridges from the bushing and die/chamber, this was a different piece)

Looking at this now, It certainly looks like I went too far? Might be an illusion, but I'm pretty sure I had the bases of the cases aligned on a straight edge when I took the picture.

The newly turned case on the right chambered with no resistance, the fellow from league had a look and didn't see any issues.

I turned 25 of these and headed to the range feeling really good... my tenth round resulted in the next picture.
Left to right: loaded (touch point +.020") , once fired, once fired and failed.

I'll be pulling the remaining loads. I'm also going to try and cut one or two open to have a look inside, never done that before - dremel or hacksaw at my disposal.

I'm pretty frustrated at this point, open to any suggestions.

Also, my fireforming load was 27.5gr H-335 and Ginex SRP, of which one primer pierced. Guess it's time to pull the trigger off the gun and clean it up, another first!

 

[Bill Norris]

The cutter is going too far into the shoulder and weakening the shoulder/neck junction. Just kissing the shoulder with the cutter is where you need to be. Your first pic is about where I like to stop. Sounds like you may have other issues with the die.

 

[Eudean]

Read neck turning basics article listed under articles.

 

[243winxb]

https://www.accurateshooter.com/technical-articles/neck-turning-basics/

I full length size brass using a standard die. The expander opens the case mouth before turning.

 

[Mike Casselton]

It looks like your cutter angle doesn't match the shoulder angle of your brass.

 

[joshb]

It also looks like your cutter is the wrong angle. Picture the inside surface of your brass mimics the outside surface with a uniform thickness in between.

 

[mikecr]

Did you want to lengthen your necks like this? Holy crap!
You cut way into shoulders,,

I take it this is 220 russian. You need a better die to lower the neck ~42thou, and a way lower angle cutter.
Good turn:

You're cutting so much thickness that you really need close to correct cutter angle(slightly higher angle than parent) so that you don't harshly dig into the shoulder

 

[Clancy]

Definitely something wrong with your sizing die, or at least the setup.

Don’t turn cases that have been sized with a bushing die, because this exact thing can and will usually happen.


This time:

Make sure the cutter angle matches the shoulder angle, or is greater (some guys use a 45° on everything.) Then, run new cases over the expander mandrel, trim to uniform length and make your first and second cut, barely kissing the shoulder. If the angle matches, it’s sure easier to tell when you’re kissing the shoulder. I don’t bump the shoulders before turning but some do. They’re so close it doesn’t matter to me.

 

[Mike Casselton]

The cutter angle looks to be close to 40°

 

[jobhopper66]

For what it's worth when I first started turning necks 25+ years ago I practiced on some 243 cases rather than on my 220R cases. I certainly spoiled quite a few in the learning process but it was a far cheaper way to learn than wrecking Lapua brass.

 

[Bronsin]

Fire forming method #1 is your friend.....

You are being redirected...

 

[6BRA]

bushing dies and neck turning.....hmm.

 

[MikeRu]

It looks like your cutter angle doesn't match the shoulder angle of your brass.

Or an option is to make your cutter angle a few degrees larger than the shoulder angle. That helps avoid creating a ridge on the shoulder. K+M Precision is helpful.

 

[Field_2_Fork]

Wow, thanks for all the replies. I haven't had time to digest them quite yet but a quick glance shows some common themes.
I have already read the mentioned articles, but will read them again.
I will try and confirm what angle of cutters I have, might be difficult to do.
Here is a sectioned case, both before and after firing. Got very thin in the shoulder for sure.




Many thanks for the suggestions.
I thought I had this under control but obviously not. Reading only gets you so far.

 

[Field_2_Fork]

Did you want to lengthen your necks like this? Holy crap!
You cut way into shoulders,,
View attachment 1445922
I take it this is 220 russian. You need a better die to lower the neck ~42thou, and a way lower angle cutter.
Good turn:
View attachment 1445928
You're cutting so much thickness that you really need close to correct cutter angle(slightly higher angle than parent) so that you don't harshly dig into the shoulder

Ya, that top picture is scary looking. I'm not sure how I didn't see how different they had become, embarrassing actually.

 

[Field_2_Fork]

bushing dies and neck turning.....hmm.

With the bushing removed shouldn't the die push the shoulder back like normal? Mine (Hornady Match grade) seems to have a sharp edge inside that just cuts into the shoulder.

 

[6BRA]

With the bushing removed shouldn't the die push the shoulder back like normal? Mine (Hornady Match grade) seems to have a sharp edge inside that just cuts into the shoulder.

And then what? Mandrel....? And hope the bushing bulge is gone...? I'm not starting this argument again....

 

[Field_2_Fork]

And then what? Mandrel....? And hope the bushing bulge is gone...? I'm not starting this argument again....

In my situation, I wasn't able to chamber the round when only a slight turn was done to the shoulder. I tried to bump the shoulder (after turning) but the die pushed/cut into the shoulder. That's why I took a bigger bite with the turner, then the round would chamber. But obviously I went too deep.

I'll add that in an video online, Jack Neary talks about using a .255 bushing when fireforming after turning. But are you saying you can't use a bushing after turning?

 

[piie]

I use the Redding competition set on 3 calibers, none of them size the neck all the way down to the shoulder, only about 2/3. Are you sure your bushing die is setup correctly?

 

[WSnyder]

You turned too far. Turn just enough into the shoulder to get a clean radius with no sharp edge. Once that’s done bump the shoulder just until the case chambers with a slight resistance. You can use a bushing or not in the die after turning, won’t matter. You are just trying to bump the shoulder enough to chamber without a lot of resistance but leaving a little for fireforming. After the initial firing is done you’ll go back to a normal bushing with slight shoulder bump with clearance.