Go Back   Alberta Outdoorsmen Forum > Main Category > Guns & Ammo Discussion

Reply
 
Thread Tools Display Modes
  #1  
Old 09-10-2019, 04:34 PM
260 Rem 260 Rem is offline
 
Join Date: Nov 2009
Location: East Central Alberta
Posts: 8,315
Default Dealing with “Doughnuts”

I typically choose bullets that seat before contacting the dreaded doughnut, but my most recent build with short freebore requires deeper seating so I must deal with it. For those reloaders not familiar with the term, it refers to band of brass that builds up inside the neck-shoulder junction...the end result of which is to reduce the inside diameter of the neck at that point ... which can result in inconsistent neck tension which will affect consistency.
A friend that is schooling me regarding how to eliminate the formation of doughnuts contends that “doughnuts never sleep” and once they develop, are near impossible to eliminate. Makes sense to me.
First, the doughnut is formed when brass “flows” forward as it is fired. At the “pinch point” (the shoulder-neck junction), it creeps into the neck which makes the neck wall thicker at that point ... and then gets forced to the inside of the neck at that point, as the neck gets resized in the die. This doughnut can not be seen on the outside of the brass because it is forced to the inside by the resizer die. The best indication that it is happening occurs when the reloader notices the bullet seats easy until it contacts the doughnut, and then manifests itself with stiffer resistance.
The ‘remedy’ I am using is to turn the neck far enough so it “bites” into the shoulder area. The desired result is to “thin” the brass in that area so when it flows forward, it does not result in a thickened neck wall.
Any other strategies out there?
__________________
Old Guys Rule
Reply With Quote
  #2  
Old 09-10-2019, 04:58 PM
Pathfinder76 Pathfinder76 is offline
 
Join Date: May 2007
Posts: 15,777
Default

Two ways, one is the way you are doing it, but K&M also sells cutting/reaming pilots. Expand necks to the donut with a mandrel and then use these cutting pilots as you also outside beck turn into the neck shoulder junction. This will eliminate them forever. The next way is to order custom dies. Minimal body sizing has eliminated the doughnut issue for a couple of friends of mine. I have dies on order for that purpose. It has not just helped, but eliminated them.

This is why cartridges like the 6.5 Creedmoor with extremely consistent tolerances between brass, chambers, and dies are nice. No doughnuts.

I also use pin gauges to check for doughnuts and this is all I will say on the subject.
__________________
“I love it when clients bring Berger bullets. It means I get to kill the bear.”

-Billy Molls
Reply With Quote
  #3  
Old 09-10-2019, 05:55 PM
HW223 HW223 is offline
 
Join Date: Feb 2010
Posts: 256
Default

Quote:
Originally Posted by 260 Rem View Post
I typically choose bullets that seat before contacting the dreaded doughnut, but my most recent build with short freebore requires deeper seating so I must deal with it. For those reloaders not familiar with the term, it refers to band of brass that builds up inside the neck-shoulder junction...the end result of which is to reduce the inside diameter of the neck at that point ... which can result in inconsistent neck tension which will affect consistency.
A friend that is schooling me regarding how to eliminate the formation of doughnuts contends that “doughnuts never sleep” and once they develop, are near impossible to eliminate. Makes sense to me.
First, the doughnut is formed when brass “flows” forward as it is fired. At the “pinch point” (the shoulder-neck junction), it creeps into the neck which makes the neck wall thicker at that point ... and then gets forced to the inside of the neck at that point, as the neck gets resized in the die. This doughnut can not be seen on the outside of the brass because it is forced to the inside by the resizer die. The best indication that it is happening occurs when the reloader notices the bullet seats easy until it contacts the doughnut, and then manifests itself with stiffer resistance.
The ‘remedy’ I am using is to turn the neck far enough so it “bites” into the shoulder area. The desired result is to “thin” the brass in that area so when it flows forward, it does not result in a thickened neck wall.
Any other strategies out there?
Cut the neck to the proper length and angle at the junction so when it’s fire formed it’s a smooth transition into the shoulder, if the die and chamber are matched there will be almost no case growth and the problem will not occur , we fire on average 10X+ Per case in a 2 day match and the growth is normally , 0-.0003
Reply With Quote
  #4  
Old 09-11-2019, 11:22 AM
32-40win 32-40win is offline
 
Join Date: Oct 2010
Location: Near Drumheller
Posts: 6,733
Default

Haven't actually used any of it yet, but over the last few yrs have been slowly acquiring the neck turning/reaming goodies, finally acquired the lathe unit from 21st Century last month. Sometime this winter I'll set it up and run some, then see what it does or doesn't do for me anyway. I've been working on buying the cutters and mandrels for inside and out over time, guess it is now time to get at 'er. Something new to experiment with. Some people say it makes some differences, some not so much, don't know til you try it. I think I am done with buying reloading tools now. Famous last words.....
__________________
You should also be a member;
CCFR
CSSA
Reply With Quote
  #5  
Old 09-11-2019, 12:35 PM
260 Rem 260 Rem is offline
 
Join Date: Nov 2009
Location: East Central Alberta
Posts: 8,315
Default

All I can say is buy good stuff. I have been using the “standard” expander buttons and turning with a Lyman neck turn tool. I am finding it very challenging to accurately change the cut depth with the Lyman because there is too much play in the cutter adjustment mechanism. I would not recommend the Lyman tool.
__________________
Old Guys Rule
Reply With Quote
  #6  
Old 09-11-2019, 12:56 PM
qwert qwert is offline
 
Join Date: Jan 2012
Posts: 2,443
Default

Quote:
Originally Posted by 260 Rem View Post
All I can say is buy good stuff. I have been using the “standard” expander buttons and turning with a Lyman neck turn tool. I am finding it very challenging to accurately change the cut depth with the Lyman because there is too much play in the cutter adjustment mechanism. I would not recommend the Lyman tool.
What is the specific make & model of sizing die you are using?
What is the specific make & model/type of expander button you are using?
Reply With Quote
  #7  
Old 09-11-2019, 02:04 PM
32-40win 32-40win is offline
 
Join Date: Oct 2010
Location: Near Drumheller
Posts: 6,733
Default

21st Century lathe setup isn't a cheap investment for 5 cartridges, but, they have all the shoulder angle cutters, reamers, shellholders, expandable to a trimmer with a different toolhead and a lever kit. I started by buying the neck turning head and then adding the mandrels and cutters, as I decided what I wanted, easy changing out cutters and adjusting it. Have played with all of that a couple of times. I saw the lathe and hummed and hawed over that for a year or two, decided to get it while I still have an income.
I could have just bought Forster add-ons for my trimmer, decided this was a better way to go. I see Hornady has a neck turning kit out now, forget exactly, but, I think you can convert the concentricity tool instead of buying the whole new setup.. I bought the neck thickness gauge addon for mine, pretty reasonable, works nicely. cheaper than a tube mic that is any good.
__________________
You should also be a member;
CCFR
CSSA
Reply With Quote
  #8  
Old 09-11-2019, 02:04 PM
marxman's Avatar
marxman marxman is offline
 
Join Date: Feb 2013
Posts: 1,844
Default

I’m sorry I ever heard of the doughnut I’ve been waiting years for it to cause me problems
Reply With Quote
  #9  
Old 09-11-2019, 03:20 PM
260 Rem 260 Rem is offline
 
Join Date: Nov 2009
Location: East Central Alberta
Posts: 8,315
Default

Quote:
Originally Posted by qwert View Post
What is the specific make & model of sizing die you are using?
What is the specific make & model/type of expander button you are using?
I am making 30-284 brass from 6.5 - 284 Lapua. Chamber has 0.330 NK. Steps are
*open NK using Hornady expander buttons ... 6.5mm>7mm>30 cal
-yields outside NK diameter 0.3335
*resize with 0.334 bushing in Redding type S die to insure NK is straight
*expand neck with 30 cal button to fit the 30 cal mandrel on the FORESTER NT tool
*trim to length 2.140 /chamfer
*turn NK with 30 cal mandrel in FORESTER NK turn tool (bite into shoulder)
NOTE: MY apology to Lyman as I mis-stated the tool is Lyman but it is FORESTER —damn yellowish stuff all looks the same.
-yields OD on NK of 0.325
* seat bullet > NK OD of loaded round is 0.327
*fire form > resize with 0.325 bushing > reload (seated with bullet, NK OD is now 0.3285)
__________________
Old Guys Rule

Last edited by 260 Rem; 09-11-2019 at 03:31 PM.
Reply With Quote
  #10  
Old 09-11-2019, 03:21 PM
260 Rem 260 Rem is offline
 
Join Date: Nov 2009
Location: East Central Alberta
Posts: 8,315
Default

Quote:
Originally Posted by 260 Rem View Post
All I can say is buy good stuff. I have been using the “standard” expander buttons and turning with a Lyman neck turn tool. I am finding it very challenging to accurately change the cut depth with the Lyman because there is too much play in the cutter adjustment mechanism. I would not recommend the Lyman tool.
My apology to Lyman —- I mis-stated the brand ...it is in fact a Forester NK tool
__________________
Old Guys Rule
Reply With Quote
  #11  
Old 09-11-2019, 04:13 PM
DLab DLab is offline
Shooting Xs
 
Join Date: Sep 2009
Location: Medicine Hat
Posts: 836
Default

The 21st. Century turner is nice,I use for both my BR's.After expanding 6BR. up to .30 BR though, the standard .30 cal. expander mandrel from 21st. does not expand enough to make allowance for neck spring back to allow proper fit on the turning mandrel,too tight of tolerance creating heat from excessive friction.
Also affects wall thickness uniformity.
PMA Tools makes a set of Mandrels specifically to deal with this known issue with .30BR case forming that fit the 21st. expander die,they also make a very good neck turning tool.
Anyway ,this set up deals nicely with the donuts formed during the sizing operation and with the proper cutter angle just touching the shoulder lightly helps delay the inevitable brass migration to the neck base after repeated firings IMHE.
Some where between 8-12 firings I usually give the necks a quick check ,turn if needed again,then anneal.
A light skim turn to uniform neck wall thickness on any cartridge case is a good procedure.


And that's Forster NK tools there 260,knew what you meant ,though.
Reply With Quote
  #12  
Old 09-11-2019, 04:46 PM
qwert qwert is offline
 
Join Date: Jan 2012
Posts: 2,443
Default

Quote:
Originally Posted by 260 Rem View Post
I am making 30-284 brass from 6.5 - 284 Lapua. Chamber has 0.330 NK. Steps are
*open NK using Hornady expander buttons ... 6.5mm>7mm>30 cal
-yields outside NK diameter 0.3335
*resize with 0.334 bushing in Redding type S die to insure NK is straight
*expand neck with 30 cal button to fit the 30 cal mandrel on the FORESTER NT tool
*trim to length 2.140 /chamfer
*turn NK with 30 cal mandrel in FORESTER NK turn tool (bite into shoulder)
NOTE: MY apology to Lyman as I mis-stated the tool is Lyman but it is FORESTER —damn yellowish stuff all looks the same.
-yields OD on NK of 0.325
* seat bullet > NK OD of loaded round is 0.327
*fire form > resize with 0.325 bushing > reload (seated with bullet, NK OD is now 0.3285)
I quite like the Hornady tear-drop shaped expanders, (and the longer taper Lee, after proper finishing & polishing) especially for significant up sizing or forming false shoulders.

The Type S ‘buttons’ are longer and smoother than typical RCBS, but IMHO they are not as suitable as the Hornady or Lee if significant expansion is required.

Redding makes a solid carbide, free floating, ball expander for their Comp series which IIRC can also be used in the Type S body.

Some report reduced donut growth when using a good internal expander.
If the correct neck bushing is used, the final drag of the expander can be very low, and hopefully just enough to smooth any incipient donut.

I am somewhat puzzled your initial loading neck OD is 0.327” and subsequent loading is 0.3285”.

Good Luck, YMMV.
Reply With Quote
  #13  
Old 09-13-2019, 08:28 AM
andy1 andy1 is offline
Banned
 
Join Date: Jan 2017
Posts: 182
Default

K&m has been doing this for the benchest community for decades. Check them out.
Reply With Quote
  #14  
Old 09-13-2019, 08:35 AM
DLab DLab is offline
Shooting Xs
 
Join Date: Sep 2009
Location: Medicine Hat
Posts: 836
Default

Quote:
Originally Posted by andy1 View Post
K&m has been doing this for the benchest community for decades. Check them out.
Yup ,another very good Brand name with quality tools as Chuck previously mentioned also.

Last edited by DLab; 09-13-2019 at 08:54 AM.
Reply With Quote
  #15  
Old 09-13-2019, 09:04 AM
260 Rem 260 Rem is offline
 
Join Date: Nov 2009
Location: East Central Alberta
Posts: 8,315
Default

Thanks for pointing to the K & M ... I see X-Reload sells them. In the meantime, I purchased a set of shims to use with the Forster.
__________________
Old Guys Rule
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 07:35 PM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.