Donuts forming 0.050" in front of shoulder?

[asauer]

I am wanting to get into long range shooting, so a friend and I had identical 300WSMs built on Winchester 70 long actions.
Load development went great- I only fired 16 rounds and found a load I figured would be great to try at longer range than the 100 yards I was currently at.
I went to load more with virgin cases, but figured I'd better check out my once fired and ensure everything was good to go with them. This is where I ran into problems...
I'm running a 0.340" neck chamber. My Norma brass measures 0.338" on a loaded round. I was going to try to get away with no-turn necks until this problem turned up. I'm getting donuts, and the COL to the lands is 3.110". I'm measuring this with the handy chamber gauge made using the reamer. Obviously this puts a 208 A-Max well past the neck/shoulder junction.
Two things are working against me here: upon closer inspection of my reamer, it was improperly ground. There is excess radius transitioning from the shoulder to the neck. Basically, instead of exactly 0.340" for the full length of the neck, the last little bit leading into the shoulder is maybe 0.343". The second problem is using my Forster FL sizing die, in order to set the shoulder back 0.002" (again using the custom chamber gauge), that "excess" neck is being shoved to the inside of the neck...

I thought I'd turn necks and try to cut into the shoulder to prevent and/or eliminate donuts, before I resign myself to having the freebore lengthened. I turned to 0.335" (measured on a loaded round) using one fired case, and test fired it. I couldn't feel any donut using pin gauges with 0.001" increments. I thought I was onto something, so I FL resized again and used a 21st century mandrel and neck turning tool (yes, the cutter has a 35° bevel) to cut the necks a second time. A little bit of material was removed everywhere, except for where the donut was! I resized the case again and proceeded with the pin gauges. A 0.305" pin gauge drops all the way through, while a 0.306" gauge is a very snug fit just at the donut. In fact, I have to give it some pressure to get it through.
This all leads me to the following questions:

A) Was more material removed on the second pass because of the work hardening since the first turning?
B) Even though that donut causes me to have to force the case onto the turning mandrel, I assume it is not tight enough to force the donut to the outside where I can cut off the last pesky 0.0005" or so?
C) My necks are approximately 0.270" from case mouth to shoulder. Using a pin gauge, I measured the depth in where the gauge hits the donut at 0.221" or so. WHY is the donut 0.049" away from the neck/shoulder junction? This case has only grown 0.001" in three firings. What am I missing?
D) Is it reasonable to assume I may be have to scrap the brass I've already fired, but if I neck turn new cases down to 0.335" or so and, ensuring I cut into the shoulder enough, have success avoiding the donut? Or does my FL sizer die/reamer issue preclude this?
E) I'm sure I know what the answer will be, but is it in my best interest to just put everything on hold while I wait for the throat to be lengthened so I can get the bullet up and out of this problem area? I have a separate throating reamer already...

Sorry for the long spiel, and thanks for your help.

 

[expiper]

OP....slide a bullet in a un sized case and see what the length is with it sitting on the donut,,,that is as short as you can load em,,,,,then measure the length of the bullet sitting on a re-sized neck ,,,the diff is the ammount of shank that is available for you to use,,,,I usually find the donut to be ~.035" on most 6mm cases,,,(remember a donut is "fat" ,,,) your dims make sense to me,,,,,if this is tooo short and robs case capicity ,,,,you should throat it deeper,,that way the donut wont matter ,,,,note the reamer dims and make your new reamer to this new appropriate length,,,Roger

 

[asauer]

expiper,

Thanks for the reply. If you look at the picture, you'll see what has me puzzled. "My" donut appears to just be a narrow bump, completely forward of the neck/shoulder junction. It flattens back out before that spot.

 

[asauer]

Also, I've already got plenty of case capacity with my setup now- extending it certainly won't hurt any.
My velocities are probably low- with the unturned necks I was getting a little bit of primer flowback into the bolt face. They were still rounded, but that was cause for me to stop at 65.0. I didn't have a chronograph initially...
Now that I've tried the necks at 0.335" on a loaded round, this primer cratering is gone. I'll try to get the Oehler back out tomorrow.

PS this is an unbushed bolt face and the barrel is a 30" 1-10 Bartlein 5R which currently has a Harrell's brake on it. Should I try for higher velocity once this is all sorted out?

 

[CatShooter]

A simple solution is to use a Forster Bump die to manage the shoulder/headspace, and adjust the bushing short so the "donut" does not appear.

The reamer looks very rough.

 

[asauer]

A simple solution is to use a Forster Bump die to manage the shoulder/headspace, and adjust the bushing short so the "donut" does not appear.

The reamer looks very rough.

Catshooter,

That bushing bump die is EXACTLY what I wanted to get to fix this problem, but I could not find any in stock for a 300WSM. Also, am I correct in that they do not size the base at all? I'm new to the whole precision shooting stuff, so I don't know if that will be a problem.

 

[CatShooter]

A simple solution is to use a Forster Bump die to manage the shoulder/headspace, and adjust the bushing short so the "donut" does not appear.

The reamer looks very rough.

Catshooter,

That bushing bump die is EXACTLY what I wanted to get to fix this problem, but I could not find any in stock for a 300WSM. Also, am I correct in that they do not size the base at all? I'm new to the whole precision shooting stuff, so I don't know if that will be a problem.

I sent you a PM with a source that can ship on Monday. Good price too.

The bump die does not touch the base OR the body - it only nudges the shoulder (and sizes the neck if a bushing is in place).

 

[asauer]

Thank you, sir. So I may as well add a body die to the order?

In the meantime, I loaded three rounds with new brass @ 0.335" loaded diameter. We'll see what the donuts look like on that.

 

[CatShooter]

Thank you, sir. So I may as well add a body die to the order?

In the meantime, I loaded three rounds with new brass @ 0.335" loaded diameter. We'll see what the donuts look like on that.

Might as well....

 

[JohnMill]

You can check Whidden dies too. For a popular cal like that he prolly hasit. He also has two different styles. FL with a neck bushing and shoulder bump with a neck bushing though I may be wrong as I've only bought the bump dies.
John

 

[Mega]

I have never played with or seen a 300WSM but I'm looking at the photo of the case neck inside and out, plus the shoulder and I can see what I believe is faults in case prep.

Maybe I'm totally wrong but what are the rings around the shoulder and it looks like there is still surplus material around the outside of the neck in the neck/shoulder junction.

I have never had a case that has had a donut so I perhaps don't know what I'm talking about but to me it looks like the initial case prep before neck turning was not done correctly and perhaps it wasn't turned right to the shoulder and that material on firing has moved to the inside. It just doesn't look correct and I doubt if any Die will fix the problem now.

I'm only going off a Cartridge Case Diagram from the Berger Reloading Manual but isn't a standard 300WSM supposed to have a neck diameter of 0.3441" so in my mind FLS new cases with a standard die and make all the same shoulder length then trim to a standard, then turn all necks right to the neck shoulder junction plus a tad before fire forming. Going on the photo that doesn't look to be the case.

The mention of the chamber not being correct is yet another problem that needs to be corrected. Are the rings caused by the bad chamber reaming...???

 

[ridgeway]

What is the true OAL of your chamber? Maybe the end of your mouth is contacting the inside of the chamber and pushing excess to form the donut. Trim back some?

 

[asauer]

Mega,

I did not turn necks before the first firing.

After the first firing, I cut the necks down to 0.337 and ran the full length of the neck and into the shoulder a healthy amount. I think what you're seeing is that problem area wanting to spring back.

 

[asauer]

What is the true OAL of your chamber? Maybe the end of your mouth is contacting the inside of the chamber and pushing excess to form the donut. Trim back some?

My cases are still plenty short of the end of the chamber in the neck- I'd bet I have about .010" to go. These cases came out of the box shorter than the "trim-to" spec and have not grown appreciably.

 

[johara1]

Get a full length die, not a bushing die. if you turn necks get the carbide mandrel, run your expander mandrel in till you just touch the donut area. Run the carbide mandrel in and cut the donut out. Then use a bushing die…….. no big deal……. jim

 

[asauer]

Get a full length die, not a bushing die. if you turn necks get the carbide mandrel, run your expander mandrel in till you just touch the donut area. Run the carbide mandrel in and cut the donut out. Then use a bushing die…….. no big deal……. jim

I'm currently only using a regular FL sizing die. No bushings. And I've been using a 21st century TiN coated expander mandrel and neck turning mandrel.

 

[Mega]

I did not turn necks before the first firing.

After the first firing, I cut the necks down to 0.337 and ran the full length of the neck and into the shoulder a healthy amount.

I think this may well be the start and cause of your problem.

Whatever brand these cases are, what is the outside neck diameter around the pressure ring of a bullet loaded say with the base half way down the neck...???? Is the Berger dimension of 0.3441" correct or have they made a mistake with these 30 cal short magnum dimensions....??

Irrespective of these dimensions did you FLS the case then use an Expander Mandrel to fit your Neck Turner to expand the case to the neck turner required tollerence fit for proper neck turning..?? The idea here being that the whole of the neck right to the shoulder is expanded so the outside cut is correct and the neck thickness is completely even the whole way to the shoulder. That is what looks wrong to me from the photo.

Again, what are all the rings around the shoulder area...??

 

[asauer]

My particular lot of Norma is 0.338" on a loaded round, unturned.

The photo of this case very well could be wrong, since I attempted to neck turn after I had already fired them.
As a test, I've done exactly as you just asked (on new brass) and I'll see how they look after firing the first time.
The rings around the shoulder are from the chamber. It is a little rough, but looks greatly exaggerated due to the lighting used so i could clearly show the inside of the neck. It isn't that bad.

 

[asauer]

So I took three new cases and performed the following:
A) FL size
B) Ensure all three cases were the exact same length
C) Expanded necks using 21st Century mandrel die
D) Turned necks in two stages (light final cut) to 0.335" loaded diameter (chamber = 0.340"). I cut up on to the shoulder quite a bit.
E) Loaded and fired

I still have a donut after FL sizing. A 0.305" pin gauge will cleanly drop through. A 0.306" will not, unless pushed with some force.

It looks like my best bet is to have the throat lengthened so I can just ignore this problem after getting the bullet out of this area. Thanks for your help everyone.

-Andy

 

[johara1]

Get a full length die, not a bushing die. if you turn necks get the carbide mandrel, run your expander mandrel in till you just touch the donut area. Run the carbide mandrel in and cut the donut out. Then use a bushing die…….. no big deal……. jim

I'm currently only using a regular FL sizing die. No bushings. And I've been using a 21st century TiN coated expander mandrel and neck turning mandrel.

Now you have that, call John at 21st Century and get the adapter to a K&M mandrel and order a carbide mandrel from K&M it has a cutter on the front and it will take the donut out…… PM me if you don't understand or need a little help …….. jim