Please educate me about outside neck turning vs. inside neack reaming

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Kosh75287

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When a smaller bore bottle neck case must be made from a larger bore case, I can readily imagine that the case neck can thicken enough to cause bullet seating/chamber pressure problems, etc.

It appears that the remedy for this is to remove some of the brass at the neck to thin it. Unless I'm completely confused about this, the necks can be thinned by turning the outside of the neck, or by removing a bit of the inside of the neck. Is one method better/easier/safer/whatever than the other?

My trepidation about outside neck turning is that the outermost bits of the brass case are being removed, creating a "step" between the top of the shoulder and the base of the neck. I surmise that, upon firing, the "step" is reduced in size or disappears altogether, as the brass flows during its containment of the (usually) 40,000 + p.s.i. being suddenly created as the powder burns. I could be incorrect in this, and if a "step" remains, it seems like a GREAT place for the case to fail in the chamber.

Would removing brass from inside the neck render new cases that are structurally more sound? Is the difference in case strength for the 2 methods worth mentioning? I'm asking these questions in the context of the "normal" range of chamber pressures, say from 30,000 psi to 60,000 psi (I'm not trying to set any new SAAMI MAP standards here, and I do my level best to stay south of the 60Kpsi level in my reloading endeavours).

Dive in, y'all. This is a subject on which I no so little, that I can't even say with certainty what I don't know.
 
OK i'll give basics and Uncle nick can come in here with all his great charts and diagrams and get to the real core of the issues .

When necking down like 308 to 243 . The brass does not extrude out the neck making it longer or not completely . It pushes down towards the base of the neck at the shoulder while at the same time the body and shoulder are trying to extrude it's displaced brass out through the neck . Well as you can imagine you now have brass flowing in each direction and where it meets ( top of the shoulder , base of the neck ) it gets thicker . Well you have the die on the outside of the case keeping it from distorting outward so the brass distorts , gets thinker on the inside of the case . This leaves what's known as a "donut" on the inside of the case at the base of the neck/top of the shoulder . NO amount of neck turning can fix this . You must remove it by reaming it out with a neck reamer . That's my understanding of it as I've read about it . I've never Necked anything done or needed to ream a neck so this is just from what I've read . Others will either come along and say how right or wrong that is .

Neck turning is a whole other animal .
 
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More about what needs to be vs ease of doing it. As in, if the inside is the wrong diameter it gets reamed. If the neck is just too big, it gets turned. Sometimes you need to do both.
Chamber pressures make no difference. 60,000ish is usually a max load anyway, but it's about the load, not the case.
 
Outside turning reduces the neck to whatever thickness measurement you set between the cutter and mandrel. Neck reaming is a simpler process of running a specific diameter cutter into the case neck. No guaranty the reaming process will be centered so necks may be thicker on one side.
I've outside turned a lot of cases that showed the cut only 1/2 way around(the thick side).
 
That link is interesting to me . I never considered sizing down a case so far down the body that the body of the case was now the new neck . I can see how that would cause problems with the neck wall now being to thick because it was once the body of the other case .
 
Even down-sizing 30-06 to 25-06 (which I do) can cause a problem.

I discovered a potential for constriction at the newly formed neck junction when using the Forster collet trimmer with my drill press. I put the appropriate 22 cal pilot in the cutter and chucked it in the press.

I then "trimmed" the long neck 22 cartridges by dropping the cutter onto the case guided by the pilot but when the pilot got close to the shoulder it would stop before it got to the trim length I needed because the inside of the neck was constricted.

I had to pull the brass out and open the neck with the K&M expand iron I use with the neck turn tool. Back on the drill press and I could trim to the needed length.

I was curious if I had removed to much material at the neck/shoulder junction so I cut a few in half to inspect. To my delight the material at the end of the cut (neck/shoulder junction) was thicker than the turned neck thickness. I did not create a weak point in the brass.
 
Dive in, y'all. This is a subject on which I no so little, that I can't even say with certainty what I don't know.
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Kosh75287, I read through the responses, I do not believe you are going to be better off after sorting through them than when you started.

I have cases when fired in the correct chamber will never form a donut. Then there are artifacts. I form cases when fired the case has absolutely no memory of what it was before firing, but, there are artifacts. Then there is fire forming, I do not do a lot of fire forming, when I fire a case it is ejected as 'once fired'. Again, there is shorter and longer.

Then there is that thing about necking up and or down, I measure before and again after.

F. Guffey
 
A long, long time ago I had a 243 and access to once fired 7.62x51 brass @ 3 cents each so I formed the NATO brass into 243 cases. I'd size the cases until they would fit the LEE Target Reloader's sizing/reaming chamber and then ream the inside of the neck. This worked perfectly to even, thin, and remove the "donut" from the smaller neck. All that was left was trimming and the cases were ready.
Properly removing that "donut" can be tricky.
If the case has been sized using a die with a neck expander, the "donut" area will be forced out and won't be fully removed by reaming. A smaller diameter reamer can be used after the case has been sized w/o the expander. This will fully remove the "donut" but won't guarantee an even neck.
My experience is that outside neck turning is not effective in removing the "donut" since the profile of the cutter doesn't allow the cut to get to the area at the base of the case neck.
 
formed the NATO brass into 243 cases. I'd size the cases until they would fit the LEE Target Reloader's sizing/reaming chamber and then ream the inside of the neck.
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Lee Target? I have Lee Target sets. Not one of the sets came with a sizing die, the die in the set is a neck sizing die, meaning it is a great ideal but it is nice when using a forming die and I would say it is absolutely necessary to have a full length sizing die.

The die in the Lee Target set came with a reamer and instructions. The top of the die was the guide for the reamer, there was a maximum amount of material that could be removed by the reamer and the guide had to be lubed.

Then there are donuts, I have assumed reloaders knew what a donut was and the cause. It reminds me of head space, to a reloader ever thing has head space and all gages are head space gages. I have chambers that will never create a donut, I form cases that are impossible to form without making donuts. I also form cases that have artifacts of the parent case. The artifact is not a donut. Then there is the step when turning the neck, the step is a mistake or neck turning done wrong.

F. Guffey
 
"Lee Target? I have Lee Target sets. Not one of the sets came with a sizing die, the die in the set is a neck sizing die, meaning it is a great ideal but it is nice when using a forming die and I would say it is absolutely necessary to have a full length sizing die."

I did not say how I sized the case. The parent case would have to be initially reduced in a press mounted standard sizing die.
 
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I have an interesting case.

A wildcat barrel chamber by an unknown gunsmith (.22-243 Middlestead). So there's no factory ammo period.

So .243 Win has to be necked down to .22, and the shoulder pushed inward another 10 degrees (20 to 30 degrees). Once done the case has to be fireformed to sharpen the shoulder.

The case necks do thicken some using the special (semi-custom) full length sizer that Redding stocks. Yes there is an expander rod inside.

What's interesting is that the gunsmith chambered the barrel with a wider neck to compensate for neck thickening.......you can do that with wildcat chambers, I guess.:cool:

Nevertheless I have some old LC brass that was previously necked down to .243 and fired once, that I necked further to .223. So the necks are even thicker than the smith compensated for.

For that brass I originally planned to just use a Forster special after-sizing inside reamer to to use with the sizer minus the expander. (Most inside reamers are made to ream fired cases before sizing). Forster makes a few that are sized to properly tension a bullet after sizing (perfect for reaming inside donuts). One does need to pay attention and get the correct one for your use.

The other option would be to use the expander in the die, and so moving the excess brass to the outside and turning the necks with an outside turner. This option appears at first thought to make more sense, since the first way would make ammo with thin necks that would expand on firing a bit excessive due to the oversize chamber neck. The outside turner could be adjusted to leave the necks as thick as non LC brass necks.........(clear as mud right?):D

However, I can imagine that interior donuts might be hard to pull expanders through.....so maybe that's not a such a great idea......or I could just stick with the commercial Federal/Winchester brass!:rolleyes:
 
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It is simpler than all this.

Outside turning is done to reduce neck wall thickness variation. It is done by cutting the neck wall parallel to the centerline defined by the ID surface.

Inside reaming is done to reduce wall thickness evenly from the current ID centerline.
 
and donuts?
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I have chambers that will never cause a do-nut. I form cases that cause donuts/close the inside diameter of the neck when formed.

And then I have chambers that by design form do-nuts when fired.

F. Guffey
 
You and you alone are the only one that has said anything about chambers in this thread . The chamber has nothing to do with what happens to a case when it's necked down . Not sure why you keep talking about your chambers . .
 
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