OK, I've formed up a batch of 6.5-284 to 284 and will be loading them tonight. I am aware that I should neck trim into the shoulder to avoid the donut. If I don't trim and end up with donuts at the bottom of the neck, can I simply seat up to the area but not through? My 284 is built on qa savage long action so I can seat out past 3.200 if necessary. I dummy loaded a 180 berger target and even loaded at 3.2 the bearing surface was ahead of where the donut would be. Am I going to experience problems even though my bullets don't seat deep enough to engage the donut?
Seating and the donut
- Thread starter 86alaskan
- Start date
CatShooter
86alaskan said:
"I am aware that I should neck trim into the shoulder to avoid the donut. "
I think you mean "turn", not trim - if you trim to the shoulder, you won't have any neck left.
If you turn to the shoulder, you will still have some donut - you will have to remove it IF your bullet heel touches it.
86alaskan,
I think you mean "neck-turn". If you do be sure to turn down onto the shoulder about 1/16th of an inch or so to give the brass an area to flow to to slow down or eliminate the donut forming. Be sure though that you do not let the point on the cutter grind on the neck shoulder junction ! It will weaken that area that is thin already and cause case neck separations. The donut is a problem if it can contact the bullet and apply excessive neck tension that causes pressure issues. The safe way to remove the donut and not thin out the case neck even more than what you have turned it to . Is to get an undersized neck reamer ( L.E.Wilson makes custom reamers that you can use either with or without the Wilson case trimmer) in .263 or .264 and use them on fired UNSIZED brass. Another fix is to run the .263 expander mandrel mandrel that comes with your neck turning tool down through the neck using the expander body die with the mandrel installed. You may need to buy a larger diameter mandrel and "customize it" by polishing it down to a .264 or .265 for spring back. Always test afterwards on either operation to see if the bullet will go down through the neck or when its seated that any material left after either operation will not grip or contact the bullet.
Take care!
Phil Hoham
Berger Bullet Tech
I think you mean "neck-turn". If you do be sure to turn down onto the shoulder about 1/16th of an inch or so to give the brass an area to flow to to slow down or eliminate the donut forming. Be sure though that you do not let the point on the cutter grind on the neck shoulder junction ! It will weaken that area that is thin already and cause case neck separations. The donut is a problem if it can contact the bullet and apply excessive neck tension that causes pressure issues. The safe way to remove the donut and not thin out the case neck even more than what you have turned it to . Is to get an undersized neck reamer ( L.E.Wilson makes custom reamers that you can use either with or without the Wilson case trimmer) in .263 or .264 and use them on fired UNSIZED brass. Another fix is to run the .263 expander mandrel mandrel that comes with your neck turning tool down through the neck using the expander body die with the mandrel installed. You may need to buy a larger diameter mandrel and "customize it" by polishing it down to a .264 or .265 for spring back. Always test afterwards on either operation to see if the bullet will go down through the neck or when its seated that any material left after either operation will not grip or contact the bullet.
Take care!
Phil Hoham
Berger Bullet Tech
Phil I've turned necks to the shoulder about the same amount as you mentioned with I believe a 40 degree neck turner and after about 5 firing I still get Donuts. Should we all be running the turner on the cases about every 3 firings to keep the donut from forming. Hope I said the right? This is with a 300 WSM. But I have shot some great groups at 1000 yards and had the 210 VLD's past the Donut.
Joe Salt
Joe Salt
If you're using a bushing die, chances are the donut will not affect your seating because of the nature of how much of the neck the bushing actually sizes. that being said, I would initially seat the bullets either touching or 10 thou off the lands if you're in the donut region, then consider turning the necks to get rid of the donut. if you're outside of the donut region, then no need to worry about it.
sorry, turning the necks, you're right that I don't want to trim that far. Thanks Berger tech, It's actually a straight 284 WIN that I've had to expand 6.5 brass up to, couldn't find any 284 brass. Based on my rudimentary measurements, when seated kissing the lands, my 180 berger target is no less than .025 or so from where it would even contact the donut. When lining up the loose bullet with the dummy round my bearing surface really only goes as far as the bushing does, which is about 7/8 through the neck. I built this on a LA with the seating depth and max case capacity in mind. I guess I'll run a few after I get a load worked up and see if there is a difference. I suppose I could test turn 10 cases and not turn another 10 and do a bit of a "donut" test to see if I'll have any problems.
so, I'm guessing that one didn't go all the way into battery? that's a first for me seeing that. That might be part of my concern too. I'm pretty new at the case turning and I don't want to ruin my lapua cases if I don't need to. If I can get get around not turning and be ok, I'd much rather do that. It's not a competition gun yet, maybe someday it will.
CatShooter
86alaskan said:
Are you running a tight neck that MUST be turned down, or a no turn neck, or a factorynexk.
Reason is, if you are not running a tight neck, you should not be turning that much brass from the necks to form a donut - just do a 90% skim, which will take maybe 1/2 a thou with good brass... and then go shoot it.
I'm shooting a CBI 284 barrel with their match chamber. Unturned fired necks measure .320, so I figure neck diameter at .322. My loaded unturned rounds measure .3125-.313. I'm using a .309 bushing to begin with until I can test for neck tension later down the road. I was under the impression that the donut was coming from me necking up the 6.5-284 brass to 284 and then firing without turning.
Looks to me like the angle of the cutter didn't match the angle of the case. It looks like the case that lost the neck went to deep and with the angle wrong it cut straight into the shoulder instead of kissing it. I am just judging this off of what I see on the case with the neck stuck on it. MattSG4247 said:
CatShooter
Joe Salt said:
Forster makes reamers, but not all sizes. Very fine carbide paper on a close fitting shaft or dowel will remove them, and there is no need to cut into the shoulder with the turning tool.
I used the 21 Century lathe with the angled cutter specifically for my brass shoulder angle.
I intentionally tried to stop short if the shoulder junction when turning.
So, this neck separation issue for me was a surprise. The redding bushing die seemed to create a fairly consistent and large donut on my brass. I decided to purchase a Widden FL bushing die, and now the presence of donuts has been reduced significantly.
I think the redding die would only allow the bushing to size 3/4 of the neck length, where the Widden will size the entire length.
So, I had 3 separations in 50 brass last week. Ended up scrapping all 50.
I intentionally tried to stop short if the shoulder junction when turning.
So, this neck separation issue for me was a surprise. The redding bushing die seemed to create a fairly consistent and large donut on my brass. I decided to purchase a Widden FL bushing die, and now the presence of donuts has been reduced significantly.
I think the redding die would only allow the bushing to size 3/4 of the neck length, where the Widden will size the entire length.
So, I had 3 separations in 50 brass last week. Ended up scrapping all 50.
CatShooter
86alaskan said:
If these are the specifications of your chamber neck, then why are you worried about donuts??
You should not be removing more than 1/2 of a thou from the necks and there is so much room in that neck that donuts cannot EVER be a problem - you are worrying about nothing.
Go shoot it!!
86alaskan, other perspectives on it;
Cases come new out of the box with donuts inherent to manufacture. While not linear, brass thickness tapers from webs all the way to case mouths. So neck brass near shoulders is slightly thicker than near mouths, and below necks thicker still.
When necks expand, a bit of thicker shoulder becomes neck, and necks expand on every firing whether upsizing a cal or not.
So without action, there is always a donut.
If you seat bullet bearing into donut you'll increase tension by varying amounts.
If you FL size necks you bring donut into tension even while bearing is clear.
If you ream out the thickness, you are not causing same resultant thickness all the way around(it's not turning).
So just don't do these things, and provided enough neck clearance, the donut doesn't matter.
Neck turning new brass is the best way to address donuts. Minimal body sizing is the best way to manage donuts(keep them from growing).
It's a simple plan that is not at all complicated or difficult.
You wondered if seating well above understood donut would be a problem. Truth is -it won't be -unless you make it a problem (as many here apparently do).
Cases come new out of the box with donuts inherent to manufacture. While not linear, brass thickness tapers from webs all the way to case mouths. So neck brass near shoulders is slightly thicker than near mouths, and below necks thicker still.
When necks expand, a bit of thicker shoulder becomes neck, and necks expand on every firing whether upsizing a cal or not.
So without action, there is always a donut.
If you seat bullet bearing into donut you'll increase tension by varying amounts.
If you FL size necks you bring donut into tension even while bearing is clear.
If you ream out the thickness, you are not causing same resultant thickness all the way around(it's not turning).
So just don't do these things, and provided enough neck clearance, the donut doesn't matter.
Neck turning new brass is the best way to address donuts. Minimal body sizing is the best way to manage donuts(keep them from growing).
It's a simple plan that is not at all complicated or difficult.
You wondered if seating well above understood donut would be a problem. Truth is -it won't be -unless you make it a problem (as many here apparently do).
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