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Discussion Starter #1
I'm prepping 22-250 Lapua brass with thick case necks, many over 016". Loaded cases could not be chambered after sizing due to case neck/chamber interference. According to SAAMI, 22-250 cases should be nominally .0125". Although I didn't measure bullet fit, they were difficult to seat. This is on a standard Shilen prefit barrel.

I've turned thousands of necks .001" to .002" for concentricity and fine tuning bullet grip by various methods over the years, generally by hand or with a small power drill and a classic Forester trimmer. These Lapua cases were unusually thick and required way too much metal removal by typical methods. Seems like they used 30-06 brass blanks and no post forming prep. This may be normal for Lapua 22-250 brass, I don't know. Regardless the brass was not going to chamber without drastic neck turning or machining.

In order to get the job done, I adapted a Forester collet holder and cutter shaft to a Sherline desktop lathe. I machined and polished the pilot for a custom fit and used special lubrication it to avoid seizing. A Forester collet can be extremely difficult to tighten adequately and fatiguing on the wrist, but with the collet housing mounted on the lathe tailstock, tommy bars can be used to get a positive lock on the case rim with little effort.

I turned thousands of necks, but this is the best method I've got with for accurate production turning and the only method that was going to get those thick Lapua case necks turned down in short order. It's a great $700 case trimmer so make sure want to learn use a lathe and have other projects in mind before you order one.

Once you get going, it takes less than a minute a case. Note all those brass chips from about a hundred cases.

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I do the same thing using slightly different tools...and my lathe is 14x60 . :) Turning .240 Cobra necks.
Note the 90 deg. corner ground from the pilot in the first picture. That makes it a reamer and it removes the donut as the neck is turned.

It makes a big difference when the cutter keeps going as cases are changed. Stop and go is hard on spindle brakes and slows things down.

Have you cast your chamber? How do you know how thick the necks should be?
 

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Elk Whisperer (Super Moderator)
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No offence swarfer, but how's that $1 apiece Lapua brass compare to to say RP or Hornady?

I'm asking if it makes a difference because I hafta trim my RP and Hornady every second reload.

RJ
 

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Discussion Starter #4
The Lapua brass in question is terrible. I bought it a few years back on a special deal so I'm just annoyed. All bright and shiny but unexpectedly very thick which caused my initial problem.

However, a bigger issue is that every case is banana shaped due to one side being excessively thick. Runout is .003" or worse for every case. They can't be straightened. The only thing you can do is try to re-center the neck thru machining necks outside or inside.

Brass cases are the most variable component in reloading and it's difficult to machine concentrically. Since it's all slightly off from the start, thickness varies, its flexible and hard to mount accurately so establishing and holding an center axis is just a compromise.

As a comparison all the Prvi brass I have is much more uniform, maybe only 10% is .003" or greater runout.
 

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swarfer--
You're right. Trying to straighten crooked brass is difficult, but not impossible. The secret is in the body taper. That has to be your reference and the base and mouth is 90 deg. to the centerline of that taper. As long as the barrel was chambered in a lathe, that's true.

Fireform the brass, then set up a Wilson case holder in a vee block in the tool holder of the lathe. Indicate the case holder true with the spindle, then use a small boring bar in the lathe spindle that's set to take a skim cut inside the neck, then the neck is true enough to turn the outside. That trues both neck surfaces true with the chamber walls.

The Wilson case holder is accurately ground to the design body taper of the case being worked on. It's just a stubby piece of steel with a tapered hole in the (precise) middle. Both ends of the case hang out.
.221 Fireball brass made from military 5.56 needs this and the main reason I now use nothing but civvy brass.
 

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That brass sounds bizarre and nothing like any Lapua brass I've ever had, which has never had more than 0.001" runout. Have you contacted Lapua about it?

You are off on your SAAMI spec for 22-250 brass. 0.0125" is the middle of the range for the mouth of the case. The standard allows the brass at the mouth of the neck to be anywhere from 0.01075" to 0.01475". The slightly tapered neck is 0.001" thicker at the shoulder, which you won't have after outside neck turning. Anyway, it sounds like you only needed to remove 0.00125" all around to bring it in.
 

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Discussion Starter #7
JBelk: Appreciate the suggestion for inside turning.

A typical 22-250 Lapua case after rework. Assume a 1/2 mil difference in neck wall thickness and 1/4 mil taper runout so subtract that from the indicator reading for an approximation of centerline runout of 1-1/2 mil. The case orbits around the taper.
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