Neck turning: Trying to turn full neck but seeing cutting high on shoulder (280 AI)

[1Moose]

I'm new to neck turning and am using Sinclair 4000 toolset on once-fired and FL sized Nosler 280 AI brass. The problem I'm having is that on some of my cases I see cut marks high on the shoulder (junction of shoulder to sidewall), even when the cutter isn't cutting near right at the junction of the neck to the shoulder. I am using the 40 degree cutter I purchased to match the 280 AI steeper shoulder angle. I thought I'd see a slight cut / rub where the neck meets the shoulder and stop turning there.

I bumped the shoulders .002" with Redding FL dies and used the expander ball. Before turning, I trimmed all cases to 2.519" to get uniform length, and expanded the case mouths with the Sinclair expander mandrel. From reading, this should push consistencies to the outside of the neck so they can be trimmed. The cases fit with minimal play on the turning mandrel (expander mandrel measures .001 larger diameter than the turning mandrel). It is admittedly difficult to get perfectly consistent case lengths with my Lyman hand trimmer, but I tried to keep them within a thousandth. Note that I did end up with a few cases that were cut into the shoulder all the way around (those must have been slightly shorter from my trimming is what I'm guessing), so I imagine I need to throw those out?

When you look at this case, however, why would the 40 degree cutter be cutting the top of the shoulder but not the neck/shoulder junction? Also does a case like this need to be thrown out? I turned 1/2 to 3/4 of the neck area on all of the cases to try to clean them up to improve precision (group size and velocity) in a hunting rifle with with standard chamber, trued action, and new Krieger barrel (fired cases are approx 10 thousandths larger than sized cases so not a tight chamber and don't want to turn too much and weaken the case). The runout on these cases with my normal loading procedures was annoyingly higher than on my 300WM and 260 Remington, so I took the leap on neck turning. We'll see if I regret it!

I wish I hadn't spun the necks with some steel wool as the photo would be more obvious.

Thank you for the help,

Brad

 

[PddPdd]

Does your neck turning tool's cutter have a radius to avoid creating a step where it stops cutting? From my experience, cutting into the sloped shoulder reduces case life even without a step.

 

[Mike Matteson]

I am looking almost the same thing, but I have set up with 21st Century to cut my necks. I am changing my 280AI neck to 6mm. I've been told by very informed person here at LRH, and backed up by the smith, to cut the neck to thickness before any firing of the cases and even before sizing the necks down to .243. The number that has came up with was .013 is magic number to cut your necks too. I had a reamer built to reduce the chamber size in the neck to only allow .002 expansion. (6mm-280AI) The mandrel that I gotten from 21st Ctry don't quick match the ID of the brass I have. 21st will build a mandrel for me, but I needed it yesterday. (Not a problem) The biggest problem is my smith is ready to chambering some cases and firing them. So I am going have the smith cut down the mandrel to fit the D.I. It doesn't stop there. The I.D. varies some for case to case. (I Purchased 500 case in one lot. Order in Feb and received in late Nov). I has me on the run.
Looking at your problem, My thinking you need to cut or trim the case to length first, then cut the necks to thickness to have better control. Which I will take that into account in working my case over. I had though about it, but hadn't check any case length yet. Sure going to do that now. Another step and a never ending story.

 

[1Moose]

Does your neck turning tool's cutter have a radius to avoid creating a step where it stops cutting? From my experience, cutting into the sloped shoulder reduces case life even without a step.

PddPdd, The Sinclair cutter has a sharp angle vs. a radius. Here's a picture. One of the things that is a bit surprising to me is that I can feel a bit of a ridge with a fingernail where the neck hits the shoulder junction from the trimming, and on the cases where I think I went too far into the shoulder I also feel that "catch" at the junction from the shoulder to the side (all while leaving a bit of untouched brass on the shoulder closer to the neck). Here's a photo of Sinclair cutter in turner (NT-4000).

 

[1Moose]

I am looking almost the same thing, but I have set up with 21st Century to cut my necks. I am changing my 280AI neck to 6mm. I've been told by very informed person here at LRH, and backed up by the smith, to cut the neck to thickness before any firing of the cases and even before sizing the necks down to .243. The number that has came up with was .013 is magic number to cut your necks too. I had a reamer built to reduce the chamber size in the neck to only allow .002 expansion. (6mm-280AI) The mandrel that I gotten from 21st Ctry don't quick match the ID of the brass I have. 21st will build a mandrel for me, but I needed it yesterday. (Not a problem) The biggest problem is my smith is ready to chambering some cases and firing them. So I am going have the smith cut down the mandrel to fit the D.I. It doesn't stop there. The I.D. varies some for case to case. (I Purchased 500 case in one lot. Order in Feb and received in late Nov). I has me on the run.
Looking at your problem, My thinking you need to cut or trim the case to length first, then cut the necks to thickness to have better control. Which I will take that into account in working my case over. I had though about it, but hadn't check any case length yet. Sure going to do that now. Another step and a never ending story.

Thanks Mike. I did trim to length, but I admittedly struggle a bit with getting perfectly consistent lengths with my trimmer (getting those locking collars in just the right spot on the Lyman Universal trimmer drives me crazy at times). I think I can sometimes put too much pressure when turning which can make some a thousandth shorter than the others.

 

[PddPdd]

PddPdd, The Sinclair cutter has a sharp angle vs. a radius. Here's a picture. One of the things that is a bit surprising to me is that I can feel a bit of a ridge with a fingernail where the neck hits the shoulder junction from the trimming, and on the cases where I think I went too far into the shoulder I also feel that "catch" at the junction from the shoulder to the side (all while leaving a bit of untouched brass on the shoulder closer to the neck). Here's a photo of Sinclair cutter in turner (NT-4000).

I'm not sure how you are cutting a step when the cutter appears to have an angle for the angled shoulder and a radius at the transition between the neck & shoulder. Can you post the same picture with a case installed on the neck trimmer?

 

[JMW67]

is this virgin brass if so fire one resize and try again this may very well solve your issue

 

[1Moose]

is this virgin brass if so fire one resize and try again this may very well solve your issue

Thanks JMW. This was once fired. I'll see how some of those look after the 2nd firing. After my sizing I'm getting between .001 and .0015 neck tension (after the expander mandrel), so I think I'm good to simply load these

 

[Mike Matteson]

PddPdd, The Sinclair cutter has a sharp angle vs. a radius. Here's a picture. One of the things that is a bit surprising to me is that I can feel a bit of a ridge with a fingernail where the neck hits the shoulder junction from the trimming, and on the cases where I think I went too far into the shoulder I also feel that "catch" at the junction from the shoulder to the side (all while leaving a bit of untouched brass on the shoulder closer to the neck). Here's a photo of Sinclair cutter in turner (NT-4000).

Not for sure, but will; check on it today. The other is I checked the overall case length on 10 cases. Found they varied .0065 from longest to shortest. They were from 2.522 to 2.5155 in length. I do know that my cutters is set up to have the correct angle for the AI cases or other cases that I reload for. (A different Head for that case angle) Cutting head on the 21st use a mandrel that I can set to stop the case where I want it too. The other is once I set up the cutter assembly for the at case. I don't plan on changing thickness or length of cut. The one thing, I like about this, it's making me think a little harder, and longer and what I am doing in the set up. I also have a Gen-3 case length trimmer to cut case length and bevel inside and out at the same time. It has a system you can set up to cut the case to the same length each time.

 

[1Moose]

I'm not sure how you are cutting a step when the cutter appears to have an angle for the angled shoulder and a radius at the transition between the neck & shoulder. Can you post the same picture with a case installed on the neck trimmer?

Here's an up close photo that I think shows it. It's as though there's a very slight bulge at where the shoulder and sidewall meet and the cutter is taking that down a bit. Maybe the brass simply didn't spring back there as much after the sizing operation?

 

[spladi]

The tighter the mandrel fits the opening in the neck the better, also seems that your case necks may not be axially concentric with the case from the NK / SHLD junction down . I wonder if after firing the irregularities in the thickness of the shoulder walls will be forced inward .........maybe that's the time to turn the necks ???

 

[JMW67]

Have you tried turning a unfired piece of brass to see if the same thing is happening

 

[1Moose]

Not for sure, but will; check on it today. The other is I checked the overall case length on 10 cases. Found they varied .0065 from longest to shortest. They were from 2.522 to 2.5155 in length. I do know that my cutters is set up to have the correct angle for the AI cases or other cases that I reload for. (A different Head for that case angle) Cutting head on the 21st use a mandrel that I can set to stop the case where I want it too. The other is once I set up the cutter assembly for the at case. I don't plan on changing thickness or length of cut. The one thing, I like about this, it's making me think a little harder, and longer and what I am doing in the set up. I also have a Gen-3 case length trimmer to cut case length and bevel inside and out at the same time. It has a system you can set up to cut the case to the same length each time.

I'll check out that Gen-3 case length trimmer. Thanks for the info on it.

 

[PddPdd]

Here's an up close photo that I think shows it. It's as though there's a very slight bulge at where the shoulder and sidewall meet and the cutter is taking that down a bit. Maybe the brass simply didn't spring back there as much after the sizing operation?View attachment 320189

So I'm not seeing the "step" in this turned neck like the earlier photo. This one looks pretty good to me. Or maybe the first photo wasn't a true side view so the "step" may have just been an optical illusion?