Let's talk about the "dreaded donut"

[woods]

Woods
I can't think of an action that would cause expanding brass(thinning) to SQUISH eleswhere.
Are the new(unfired) neck ODs tapered from mouth to shoulder?
Then are your formed neck ODs tapered?

I have to outside neck turn the new brass before firing so it will fit in my .313" Hart chamber. It is a complete turn with no unturned surfaces left and is consistant from mouth to shoulder with a tight fitting mandrel.

The pin gauge in the pic above slides in with the same consistancy until it hits the do-nut at the shoulder and my micrometer says that the neck brass has a consistant thickness. There is a small ridge at the shoulder/neck junction that is not there on the new cases. The OD is also very consistant and the powder blow back line is a consistant distance from the case mouth all the way around which is an indication of a consistant neck thickness all the way around.

No other explanation than the firing caused brass flow along the shoulder and formed the do-nut.

IMO

As far as reaming, I use the Forster reamer. It is .003" over caliber so I outside neck turn to a thickness that will give me .003" clearance around the neck in the chamber. After firing, the .003" transfers to inside clearance for the reamer.

The reamer shaft is the same as the outside turning mandrel shaft so it will fit in my hand held turner

that way I can trap the brass between the reamer and the outside turning blade, ream the inside and clean up the outside for a very consistant neck thickness after the first firing

usually reduces the neck thickness ~.0005"

IMO I get a better product with the full length reamer blades that will work on the full length of the neck at the same time than I did with the K & M cutter mandrel which has a cutter on the very end of the mandrel.

YMMV

 

[yawn]

Also in a 280ai Iv had to inside neck ream because of donuts in nosler 280ai brass.Fired cases are .316 od so i havent had to turn them. Iv fire formed norma brass with no donut after 4 firings and Im now onto a new box of nosler 280ai which after 4 firings have no donut. It maybe a little harder than the original cases from nosler.

 

[Mikecr]

Well Woods, you should get a prize for 'most over-complicated turning procedure' possibly in reloading history..
You should realize you don't need reamers and super accurate pin gauges to arrive wherever you're going. Just basic outside neck turning and a pre-FFing plan that produces desired results..

And the whole 'flow' perspective is completely flawed. Brass doesn't melt and smear anywhere on firing. It is rolled, stretched, wiped(with a ball), or formed right where you put it.
So your doughnut is either something overlooked w/resp to chamber to brass fitting on fire-forming, or you're assigning too much credit to pin gauge fit.

I'm sure there is a explanation for it that alot of nice pics isn't showing.

 

[woods]

Well Woods, you should get a prize for 'most over-complicated turning procedure' possibly in reloading history..
You should realize you don't need reamers and super accurate pin gauges to arrive wherever you're going. Just basic outside neck turning and a pre-FFing plan that produces desired results..

And the whole 'flow' perspective is completely flawed. Brass doesn't melt and smear anywhere on firing. It is rolled, stretched, wiped(with a ball), or formed right where you put it.
So your doughnut is either something overlooked w/resp to chamber to brass fitting on fire-forming, or you're assigning too much credit to pin gauge fit.

I'm sure there is a explanation for it that alot of nice pics isn't showing.

I'm up for prizes!

Doesn't brass flow and cause the case to elongate so we have to trim? I mean, the case is within trim length specs before firing and after firing it is too long sometimes. Or are all those trimmers just tools for an imaginary problem? I'm talking about before a sizing die ever hits them. I suppose that could come under the "stretching" description but isn't that more or less flowing?

Anyway, I can't come up with a different explanation and there is definitely a ridge at the shoulder/neck junction that is not anywhere on the rest of the neck.

So what do you think I should do pre-fireforming to alleviate the problem?

 

[rscott5028]

Mikecr -

Perhaps "flow" is a misnomer? I should've used proper technical terms like "squished".

I actually got most of my info on this matter from a reloading video put out by Jim Carmichel and Ned Kalbfleish that I got through Varmint Hunter Magazine. I may be misquoting their explanation. So, don't go flaming them. I'll have to go back and watch it again sometime. ...I hate VHS.

The good news is that the bullet usually goes pretty much where I'm aiming when I squeeze the trigger. On the other hand, I'm keen to understand why/how so as to improve.

thanks!
Richard

 

[SBruce]

Perhaps flow is the wrong term, but I too have seen brass lengthen, sometimes substantially from fireing alone. I mean, I measured the OAL before loading and again after fireing (no resize yet) and saw it "grow". This was especially prevalent in the 220 Swift case. Not so much in the 22-250's or 25-06's I've had. Testing so far shows absolutely no stretch in the 6 Long Dasher from fireing alone.?

 

[boomtube]

Mikecr is correct.

At least a PROPERLY resized case expands in diameter when fired and will often - usually? - get a tad shorter. Then, when it gets squeezed down in an FL die it will get 'squished' longer. The extra length can only go to the neck so it gets longer during sizing. That extra length comes from the case body as part of the wall moves to the shoulder while part of the shoulder moves to the neck and that creates, or may eventually create, a 'donut.'

Yes, IF a case is much shorter than the chamber, a really sloppy fit in other words, it will stretch just above the web during firing but that will not happen IF the case is properly FLsized, (or simply neck sized) for a snug chamber fit. That chamber slop and resulting stretching happens due to over-enthusastic FL sizing. Such repeated stretching may evenually case a head seperation and, possibly, a donut too. But, none of that happens because the brass "flows" under the pressure of firing as if it were putty; it isn't.

Reforming/sizing a case down to a smaller caliber, such as going from .308 to .243, puts what was neck wall into the shoulder and no donut will be formed. On the other hand, reforming up, a .243 to a .308, will put what had been shoulder brass into the neck and that IS the donut.

Reaming will remove the donut but reaming does nothing otherwise to the neck, if it was non-concentric to start with a reamer leaves it that way. I prefer to neck turn instead (I like the same Forster HOT-100 hand held neck turner as Woods uses), but using the turner requires that the donut be forced to the outside first. Annealing, followed by a Lyman M expander die usually does the turning preparation work for me.

Most of the BR donuts come from up-sizing .220 Russian to 6mm PPC. If we reform a .308/.243 to .22-250 or .30-06/.35 Whelen to .243, a part of the original case side wall becomes neck and we will get a huge donut, but not many of us do such massive case refoming as that!

 

[TOM H]

Well Woods, you should get a prize for 'most over-complicated turning procedure' possibly in reloading history..
You should realize you don't need reamers and super accurate pin gauges to arrive wherever you're going. Just basic outside neck turning and a pre-FFing plan that produces desired results..

And the whole 'flow' perspective is completely flawed. Brass doesn't melt and smear anywhere on firing. It is rolled, stretched, wiped(with a ball), or formed right where you put it.
So your doughnut is either something overlooked w/resp to chamber to brass fitting on fire-forming, or you're assigning too much credit to pin gauge fit.

I'm sure there is a explanation for it that alot of nice pics isn't showing.

I agree with you and I also thing one of the problems is that most don't understand the use of the expander mandrels like Sinclair/K&M/Hart sells that makes turning neck easier and more accurate as to neck thickness.

I think I got luck in that some BR shooters showed me how to turn neck back in the early 80's for the 6ppc.

 

[Michael Eichele]

A thought on 'flow' or brass moving forward.

If you take a brand new case, measure it's length, fire it and measure again, you will find that the length changes very very little if any at all (assuming the chamber is within good tolerences. The shoulder may move depending on headspace etc....But the overall length very little. After you full length size, you will find that the case is now longer. It is the resizing NOT the firing that causes the majority of any length increases. In fact, resizing has such an affect on case demensions, many shooters think that they are 'bumping' the shoulder when in fact they are setting it back conciderably even if it only measures .001 back from when fired. This is because the shoulder moves forward during FL sizing. If you run a fired case up your FL die and stop .010 short, pull it out and try and load it into your chamber, you will find that it likely will not fit. This is because the shoulder has moved forward. To bump it back .0005-.001, it actually has to be bumped several thousandths because it has moved forward several thousandths while being resized. Now there are exceptions to this rule. If using a tight chamber where the case cannot expand much or at least spring back to at or near specs, you may not see any forward movement or very little of it. For factory chambers and full on SAMMI spec chambers, you will see alot of forward 'flow' if you will. In this sense, Mikecr is right.

Do-nuts are often times caused by improper neck turning. If you dont turn enough brass at the neck shoulder junction, the excess brass on the out side of the neck has to go somewhere during resizing and firing. This is when it goes inside the neck. Brass needs to be turned so that a small cut goes onto the shoulder. Not too much though. When neck turning, a good mandrel should be used to run inside the neck to get the inside of the neck right. Then any flaws will be outside. When you push the flaws from inside the neck to the outside, then they can be turned and the flaws will be cut away. I like the K&M set because the neck guide has teeth in the bottom to remove any do-nuts when the neck walls are touched up. The upper end of the shank is smooth for smooth, uniform turning.

This is on main reason I like to neck turn. It isnt always about making a neck concentric with the bore but rather I prefer to have a smooth uniform neck for consistent neck tension.

If neck turing is done right, you should hardley ever, if ever see any do-nuts. I have in factory chambers when FL sizing over and over but not is good custom fitted chambers be it FL sizing or neck sizing. This maybe one instance where using an expander ball during resizing may be of any benefit as it would push a do-nut out of the way. I still prefer to neck turn and either use a body die and sperate neck die or neck size only since expander balls tend to cause runout.

M

 

[SBruce]

How much would a guy expect to pay for a pin gauge or set of gauges?

If I am understanding all this correctly, that is the only way to tell for sure if we have these donuts or not.

What other types/kinds of inside reamers have you all used to remove these donuts. I've now seen the Forster one that goes in the turner, I've seen the K&M ones that are part of the turning mandrel, but what about stand alone ones?

Again, thank you all for the responses.

 

[woods]

How much would a guy expect to pay for a pin gauge or set of gauges?

If I am understanding all this correctly, that is the only way to tell for sure if we have these donuts or not.

CDCO Machinery Corp.

this is a link to the website so you have to click on "Measuring Tools" and then "Gage Blocks and Pin Gauges"

they are up to $65.00 for the .251" to .500" from when I bought a set years ago for $55.00

 

[royinidaho]

Chiming in to say that this is a good informative thread.

I'm with Michael Eichele on this one as all of my 'donuts' have been do to improper turning with a Forster turner which is probably the worst of the bunch with its round cutter.

Donuts occurred in my work with 22 Rem and 270 Win.

I have had no donuts necking up 7mm through 375 RUM to 270 cal.

 

[TOM H]

How much would a guy expect to pay for a pin gauge or set of gauges?

If I am understanding all this correctly, that is the only way to tell for sure if we have these donuts or not.

What other types/kinds of inside reamers have you all used to remove these donuts. I've now seen the Forster one that goes in the turner, I've seen the K&M ones that are part of the turning mandrel, but what about stand alone ones?

Again, thank you all for the responses.

Here something from the BR site on the donut and how to not create them.
The dreaded doughnut..... [Archive] - Benchrest Central Forums

 

[woods]

I think you can also buy the pin gauges individually like this guy did

My Doughnut Machine is Working Fine