Neck turn gone wrong. Help please.

[dgeesaman]

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

True, it looks like it matches the 30 degree of the ppc not the 20-something of 220 Russian.

So the idea of matching the shoulder angle on the fire forming prep would require a whole other cutter. Ive only ever used a 30 deg cutter, with good success. That said, I’ve never run a .262 neck, I just skim cut mine.

The correct answer appears to be between your first two cases pictured.

David

 

[1shot]

As many have previously said, is looks you turned to far into the shoulder and did it with the wrong angle of cutter.
I hope this helps,

Lloyd

 

[Andy Work]

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?

Using a bushing die after turning is fine. You don't want to use a bushing die before turning because they don't size the entire neck, the part above the shoulder junction is unsized. Turning necks sized this way down to the shoulder junction will create a thin area.

 

[6BRA]

1st pass before fireforming to allow to chamber, do not cut into neck. Use only a nonbushing die. 2nd pass after fireforming using a non bushing die and cut into shoulder just barely. If you have a 40 deg shoulder, and using a 40 deg cutter, be very very careful, as the shoulder flattens out, very very minute movements in shoulder depth adjustments make a huge difference. At .0085 you are already very thin. My opinion, get rid of the bushing die and get a mandrel ,non bushing die combo, and anneal. Brass never flows evenly and some re-turn every 3 to 4 firings. My opinion bushings contribute to uneven brass flow. At .0085 you have already lost alot of bullet gripping force from the brass. More tension will be required.

 

[Ccrider]

Post 22, 23 and 24 covered it for you.

I will add that you may want to try foreforming without bullets using pistol powder and then turning your neck. If you do, don’t size the necks after foreforming unless you use a full length non bushing die and then a mandrel.

There are several threads explaining in detail how to fireform. The search feature is your best friend.

 

[Chris Edmondson]

I was going to suggest you cross-section a few pieces to see what's going on, looks like you've already done that. As others have said, cutter angle should be checked, it looks on the steep side to me. I'm turning on a lathe so I have full control over the cutter angle, I took K&Ms advice and use just shy of 2 degrees above nominal shoulder angle.

When I shared some cross-section pics with a shooter friend who's forgotten more than I'll ever know about the sport, he felt I did not cut enough into the shoulder. He opines that, as the brass grows, it will fill in any perceived thin area. While I agree in principal, there's a fine line between cutting too far into the shoulder, I've done that and experienced what you did where the neck disintegrated from the shoulder.

I snuck up on my shoulder cut by progressively cutting deeper and studied the cross-sections until I noted that nowhere on the shoulder had less wall thickness than nominal. It's not easy to measure, there's some shady tree in there, but, I'd rather deal with donuts than risky brass.

 

[Hugh Williamson]

Bring your gear to the benchrest match at Rosebud , we will walk you through the process and get you set up , looks as though you’ve cut to far down into the shoulder , easy to fix , if you get the neck right most other issues come from sizing dies that do not properly match the chamber

 

[Chris Edmondson]

Pictures being worth thousands of words, the one's below show where I decide to stop. The first number is the turned wall thickness, the second number is an arbitrary lathe z-axis position only valid for this turning session. I use the actual cross-section piece of brass to gage where to stop.




These two pictures shows going in another 0.005", that's where I felt I'd gone a touch too far.




Hope these help.

 

[rayporter]

do not pass up the chance to let Hugh help you!!

 

[liljoe]

I also suggest you make every effort you can to go talk with Hugh.
He can answer any questions you have and will point you in the right direction.
Joe Hynes

 

[Field_2_Fork]

Bring your gear to the benchrest match at Rosebud , we will walk you through the process and get you set up , looks as though you’ve cut to far down into the shoulder , easy to fix , if you get the neck right most other issues come from sizing dies that do not properly match the chamber

Thanks a lot Hugh, I sure appreciate that. I plan to be there for the Stampede Shoot, it will be my first time there and first match.
Looking forward to it to say the least!

 

[Field_2_Fork]

Pictures being worth thousands of words, the one's below show where I decide to stop. The first number is the turned wall thickness, the second number is an arbitrary lathe z-axis position only valid for this turning session. I use the actual cross-section piece of brass to gage where to stop.

View attachment 1446233View attachment 1446234


These two pictures shows going in another 0.005", that's where I felt I'd gone a touch too far.

View attachment 1446237View attachment 1446238


Hope these help.

Very helpful pictures, thanks for that. Mine were definitely a fair bit further yet.

 

[Webster]

Read neck turning basics article listed under articles.

Picture cutting 5-10 thou into the shoulder. Pix borrowed from Chris Edmonson post.

 

[Field_2_Fork]

I'm finally able to get back to this after being gone for a week, here's a little update from last night.
I borrowed a Redding small base die to bump the shoulder as step 1. Then all the regular steps - mandrel, turn etc. A smmall ridge still gets pushed into the shoulder when bumping, same as my Hornady die from before, I was concerned about this but I guess that's just how it is.

I have made 5 cases that all chamber freely and seem to be very consistent, happy about that.
The one question I have is about the sine wave I have in the shoulder, 28* cutter.
Not sure why this is happening, I don't have a concentricity tool. Cutter is just touching the shoulder, very smooth.

 

[liljoe]

The neck is not concentric with the shoulder. That's why it is cutting more on one side.
Most likely caused from necking up. There are ways to improve this but it can be a deep hole.
Does it make a difference on the target? Maybe?
Check your bullet runout on a few cases that are very even cut and some that are visually off after firing them.
Joe

 

[Bill Norris]

The neck is not concentric with the shoulder. That's why it is cutting more on one side.
Most likely caused from necking up. There are ways to improve this but it can be a deep hole.
Does it make a difference on the target? Maybe?
Check your bullet runout on a few cases that are very even cut and some that are visually off after firing them.
Joe

Agree and after a few firings this should level out as cases become more formed to the chamber.

 

[Field_2_Fork]

I've been trying to figure out why that started, it wasn't doing it originally. Just realized that I had put an o-ring on the mandrel die, to try and hold it in the press (no lockring on it). Possibly that is pushing the die enough to make it off center.
Going to shoot these and see what happens.