The dreaded doughnut.....
- Thread starter Joe
- Start date
S
sundance
Guest
What about movement?
My fired cases have a tight spot (donut I presume) that seems to move further up the neck with successive firings?
After fire forming (243AI) I neck size with Redding dies and a carbide expander ball. Bullet seating pressure seems consistent in both new and old brass? The load is well below max, but the tight spot continues to migrate. Any comments?
Mike
My fired cases have a tight spot (donut I presume) that seems to move further up the neck with successive firings?
After fire forming (243AI) I neck size with Redding dies and a carbide expander ball. Bullet seating pressure seems consistent in both new and old brass? The load is well below max, but the tight spot continues to migrate. Any comments?
Mike
P
Pete in Surry
Guest
Doughnuts
Last evening I was trimming some cases I had made in an 8 step process a couple of months ago. I was surprised to find that 2 of them had doughnuts in them and they have not had any charges fired in them as yet; virgin brass!
I assumed that it took fireing loads through cases to make doughnuts in the necks but realize that it must be working the necks that causes it, not the explosion. I find it interesting that some cases never develop doughnuts. Why is that true?
Last evening I was trimming some cases I had made in an 8 step process a couple of months ago. I was surprised to find that 2 of them had doughnuts in them and they have not had any charges fired in them as yet; virgin brass!
I assumed that it took fireing loads through cases to make doughnuts in the necks but realize that it must be working the necks that causes it, not the explosion. I find it interesting that some cases never develop doughnuts. Why is that true?
Bob Kingsbury
New member
Joe, do your primers (pierce) at lower amounts of powder ??????
A case will NEVER develop a donut unless you're over-sizing it. It is the shoulder brass being shoved into the neck that makes the donut. Re-setting the shoulder for any reason will likely result in a donut. There's no mystery here 
Just realize that the brass just around the corner of the shoulder is THICKER than the neck brass and the body brass is thicker yet.......increasing in thickness clear down to the base of the case.
The old saw about donuts being some sort of pressure artifact is just one of those goofy "stands to reason" things that refuses to die....it aint ABOUT pressure!
al
Just realize that the brass just around the corner of the shoulder is THICKER than the neck brass and the body brass is thicker yet.......increasing in thickness clear down to the base of the case.The old saw about donuts being some sort of pressure artifact is just one of those goofy "stands to reason" things that refuses to die....it aint ABOUT pressure!
al
Pete Wass
Well-known member
How come - -
not all of them develop the doughnut? The cases I was refering to are 284 cases that have been shortened up to 1.650. The necks are made from the case body then reamed in step 6 of 8. Same for 30 BR cases. I have found that some of them never develop doughnuts. I'm just askin is all.
not all of them develop the doughnut? The cases I was refering to are 284 cases that have been shortened up to 1.650. The necks are made from the case body then reamed in step 6 of 8. Same for 30 BR cases. I have found that some of them never develop doughnuts. I'm just askin is all.
Because if you turn deeply enough into the neck you don't get the donut at the junction. I'm not speaking for your situation but for ME the problem lies with using the mouth of the case as the stop for the neck turner........the lengths vary enough that you end up with every shoulder being stepped in just a liddle differently.
My own solution is to regrind my neckturning cutters so that the shoulder is the stop, that way I can turn clear to the shoulders and trim to length AFTER. Some times even after I've fireformed in the cases where I've had matching reamers made with different length necks. I just reground a cutter today, my neckturning tools are still out on the bench. I sectioned a couple cases too to check for shoulder thickness and neckturning depth. If you're interested I'll go down later and try to shoot a couple pix to show HOW turning into the neck eliminates the donut.
Today I tried a new way of stopping my cutter, I ground my tool to nearly match the shoulder angle and then just went up the shoulder about 50-60thou and broke the cutting edge with a dremel cutter. It's working like a charm! The reason is, I'm making 6X47L brass from 6.5 brass so I'm getting a very thin shoulder-to-neck radius, there's not much meat to work with. Normally the thicker brass behind the junction allows me to really gouge into that shoulder but not today.
So Pete, all I can say is....... I'm guessing that your donut is formed when you're making cases. If NOT, then you've got something going on later in the process that's causing you to shove the shoulders back.
The donut is NOT caused by "brass flowing forward under pressure" in any case.
LOL
al
My own solution is to regrind my neckturning cutters so that the shoulder is the stop, that way I can turn clear to the shoulders and trim to length AFTER. Some times even after I've fireformed in the cases where I've had matching reamers made with different length necks. I just reground a cutter today, my neckturning tools are still out on the bench. I sectioned a couple cases too to check for shoulder thickness and neckturning depth. If you're interested I'll go down later and try to shoot a couple pix to show HOW turning into the neck eliminates the donut.
Today I tried a new way of stopping my cutter, I ground my tool to nearly match the shoulder angle and then just went up the shoulder about 50-60thou and broke the cutting edge with a dremel cutter. It's working like a charm! The reason is, I'm making 6X47L brass from 6.5 brass so I'm getting a very thin shoulder-to-neck radius, there's not much meat to work with. Normally the thicker brass behind the junction allows me to really gouge into that shoulder but not today.
So Pete, all I can say is....... I'm guessing that your donut is formed when you're making cases. If NOT, then you've got something going on later in the process that's causing you to shove the shoulders back.
The donut is NOT caused by "brass flowing forward under pressure" in any case.
LOL
al
Boyd Allen
Active member
Al,
I have to hand it to you, your cutter idea is a great one. If I am expanding .220 Russian to 6mm and then turning before fire forming (with a 6mm bullet) I have to turn onto the shoulder so that the bolt closing force is not excessive. Even though I have gotten pertty good at "eyeballing" the depth of the cut on the shoulder, there is some variance that I can feel as differences as bolt closing effort. With your cutter design properly sharpened for my barrels' headspace,(so that I get the proper depth of cut on the shoulder) I would have a more uniform result. I understand that if I want to use a trimmer that stops on the shoulder before turning that I can set up my turner to use the end of the neck as a stop, but I like to preserve as much neck length as I can, since my chamber is 1.515 and my fire formed cases typically clean up at about 1.495. On the other hand, since my bullets come nowhere near the base of my case necks, I don't worry much about donuts.
I have to hand it to you, your cutter idea is a great one. If I am expanding .220 Russian to 6mm and then turning before fire forming (with a 6mm bullet) I have to turn onto the shoulder so that the bolt closing force is not excessive. Even though I have gotten pertty good at "eyeballing" the depth of the cut on the shoulder, there is some variance that I can feel as differences as bolt closing effort. With your cutter design properly sharpened for my barrels' headspace,(so that I get the proper depth of cut on the shoulder) I would have a more uniform result. I understand that if I want to use a trimmer that stops on the shoulder before turning that I can set up my turner to use the end of the neck as a stop, but I like to preserve as much neck length as I can, since my chamber is 1.515 and my fire formed cases typically clean up at about 1.495. On the other hand, since my bullets come nowhere near the base of my case necks, I don't worry much about donuts.
Boyd,
I do it this way:
--First, I have the chambers cut short.
--Then I bump all shoulders to exactly the same length. They vary right out of the box. I ran a sampling of the 6.5X47L brass today, only 6 random samples, and they were within a thou...... unbelievably good, even for Lapua brass.......but from lot to lot I expect variance, hence the mandatory bump.
--Then I expand up and turn, indexing off of the re-set and consistent shoulder.
It took 5 tries to get the crush right today........trial and error to make expanding up such that it would final out as a crush fit. I ended up using a Redding 6BR die with the long expander "ball" and found a setting (.012 Skips Die Shims) which final'd out and neck turned to a consistent crush-fit.
I've got two identical 6BR reamers except that one of them is a no-turn neck and is long enough to shoot no-trim. With this setup I can fireform in a varmint rifle to hammer out the neck and THEN turn and trim for the Match chamber. This works so well that I'm planning on using a similar technique for the 6X47.
I'm playing with the idea of adding an inside reaming step. I've got the reamers, just haven't taken it that far yet. For my 300WSM project I'm planning to re-set the shoulders for crush, fireform, ream and THEN neckturn. I've got .005 of brass to play with for the reaming/turning operations. I hope it's enough!
al
I do it this way:
--First, I have the chambers cut short.
--Then I bump all shoulders to exactly the same length. They vary right out of the box. I ran a sampling of the 6.5X47L brass today, only 6 random samples, and they were within a thou...... unbelievably good, even for Lapua brass.......but from lot to lot I expect variance, hence the mandatory bump.
--Then I expand up and turn, indexing off of the re-set and consistent shoulder.
It took 5 tries to get the crush right today........trial and error to make expanding up such that it would final out as a crush fit. I ended up using a Redding 6BR die with the long expander "ball" and found a setting (.012 Skips Die Shims) which final'd out and neck turned to a consistent crush-fit.
I've got two identical 6BR reamers except that one of them is a no-turn neck and is long enough to shoot no-trim. With this setup I can fireform in a varmint rifle to hammer out the neck and THEN turn and trim for the Match chamber. This works so well that I'm planning on using a similar technique for the 6X47.
I'm playing with the idea of adding an inside reaming step. I've got the reamers, just haven't taken it that far yet. For my 300WSM project I'm planning to re-set the shoulders for crush, fireform, ream and THEN neckturn. I've got .005 of brass to play with for the reaming/turning operations. I hope it's enough!
al
A slick way to get avoid donuts is:
-Take an extra shellholder and face .020-.025 off.
-Run the virgin brass through your f.l. or bump die using this shellholder
-Now neck turn, stopping your cut at the 'new' neck/shoulder junction
-Set the seating die up for about .025-.030 'jam' with your fireform bullets
-Fire 'em with a mid range powder weight
The shoulder will 'blow' foward the .020-.025 that you set it back by using the faced off shellholder. Since you neck turned to the 'setback' neck/shoulder junction, the last .020-.025 of your neck length is now 'blended' into the shoulder of the fireformed case.
You reduce the 'donut factor' becase the brass in the first .020-.025 of the shoulder is the same thickness as the case neck. The thicker brass in the shoulder of conventionally turned cases wants to 'creep' around the base of the neck easier than does brass of the same thickness as the neck.
Neckturning this way, and sizing correctly, will make 'donuts' almost a thing of the past. Even when you are not bumping the shoulder back excessively during sizing, your die can still contribute to the 'donut factor' by not being a good match to your chamber.
Here's a photo of what I'm talking about: this happens to be an extreme example of this...new brass that I'm going to fireform this afternoon for my .30 WolfPup chamber on the left and a fireformed .30 WolfPup case on the right. But this illustrates the concept pretty well. In this case, the 'blend' is fully .065 into the 'new' shoulder after fireforming.
For what it's worth. -Al
[/IMG]
-Take an extra shellholder and face .020-.025 off.
-Run the virgin brass through your f.l. or bump die using this shellholder
-Now neck turn, stopping your cut at the 'new' neck/shoulder junction
-Set the seating die up for about .025-.030 'jam' with your fireform bullets
-Fire 'em with a mid range powder weight
The shoulder will 'blow' foward the .020-.025 that you set it back by using the faced off shellholder. Since you neck turned to the 'setback' neck/shoulder junction, the last .020-.025 of your neck length is now 'blended' into the shoulder of the fireformed case.
You reduce the 'donut factor' becase the brass in the first .020-.025 of the shoulder is the same thickness as the case neck. The thicker brass in the shoulder of conventionally turned cases wants to 'creep' around the base of the neck easier than does brass of the same thickness as the neck.
Neckturning this way, and sizing correctly, will make 'donuts' almost a thing of the past. Even when you are not bumping the shoulder back excessively during sizing, your die can still contribute to the 'donut factor' by not being a good match to your chamber.
Here's a photo of what I'm talking about: this happens to be an extreme example of this...new brass that I'm going to fireform this afternoon for my .30 WolfPup chamber on the left and a fireformed .30 WolfPup case on the right. But this illustrates the concept pretty well. In this case, the 'blend' is fully .065 into the 'new' shoulder after fireforming.
For what it's worth. -Al
H
henrya
Guest
I'll second what Al Nyhus wrote and add that you can also do the same trick by turning at a larger caliber before necking down. ie - .30 caliber turned before necking to 6mm. You get the same result - a blend of the neck into the shoulder instead of a knot or donut at the junction. You just have to carefully figure out how long to make the cut.
If part of the thick shoulder material ends up in the neck - that's the donut. What you want to do is to cut out the material before it ever forms the donut. You can't do this nearly as well if you're cutting on the neck and shoulder junction at its final or finished position. Best you can do with that is to cut into the shoulder a bit which is tricky.
New brass out of the box won't let you get into the shoulder area to make the blend. The brass that needs to get cut out is hiding in the shoulder.
If part of the thick shoulder material ends up in the neck - that's the donut. What you want to do is to cut out the material before it ever forms the donut. You can't do this nearly as well if you're cutting on the neck and shoulder junction at its final or finished position. Best you can do with that is to cut into the shoulder a bit which is tricky.
New brass out of the box won't let you get into the shoulder area to make the blend. The brass that needs to get cut out is hiding in the shoulder.