In the past I have inside Bored straight Tapered brass in order to be able to make fixed ammo with Groove size Bullets on the Base. Instance, Original Sharps .45 Caliber Barrels have a .451/.452 Bore and a .461/.462 Groove. In the day when Black Powder was the rule the Paper Patch Bullets were .450/.451 Outside diameter. They would Bump right up with the Black Powder charge. I set up in a good lathe with
5C collets and turned a Sleeve to a very accurate OD and then without removing it drilled and Bored the sleeve in Place to the Taper of the Case. Then cut it off and cleaned to a length that allowed a Fired case to seat in the sleeve with the mouth of the case within about .05/.06 from the end. I could now take a Shell and insert it and just bump the base to seat it and insert the whole thing into the 5C collet and precision Bore the Inside Diameter to suit a Base Band bullet from a modified Mold to the Groove size of the Rifle. These Shot very accurately using Smokeless Powder. I also had the option to bore to a specific depth leaving a shoulder for the bullet to seat on. I have only used this method with straight Tapered shells such as 
.45 X 2 1/10" (45-70) .45 X 2 4/10" (.45-90).  .40 X 2 5/10"
.40-70 SS. Have never done it with Shouldered or Necked Brass. I suspect it could be made to work if I hade a close chamber shape and precision Bored the Neck Section to assure good support for the Boring operation. The original Sharps chambers have no Throat as they were made for Bore Size Paper Patch bullet. Just a Straight Tapered Chamber with a 45 Degree Chamfer to the Bore. This system works very well for these conditions in the Original Chambered Rifles as above.
HTH. Regards, FITZ. OLD TUCK.

Red Cent wrote on Sep 3^rd, 2018 at 1:06pm:


A collet die will iron out the flat spots, but I have never seen one that will evenly distribute an extra .002 of brass around the neck.

The imperfections of neck thickness get pushed to the inside with a bushing, to the outside with a sizing ball, mandrel or bullet.

A collet type die applying pressure to a mandrel, limits the variation and helps with concentricty within a range. I played with one and it helped with neck runout in cases that were decent to begin with, but cases reformed from other cartridges, where the body became the neck, still had excessive taper or thickness variations. Turning was the only way to correct it.

For neck turning I use an outside cutter with a neck mandrel that also has a cutting edge. So instead of pushing high spots out or causing an alignment issue with the outside cutter, they are removed. I have had less thickness variations since going to that method.

craigd wrote on Sep 3^rd, 2018 at 7:03pm:


This turner, with the pilot at the bottom. It won’t really ream the neck but will take out the high spots and if there is a donut from sizing or working up into the neck from the body. 
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You really can inside turn case necks but I have never heard of anyone doing that. 
Reaming case necks would not really qualify as turning but single point boring would.  However holding the case neck on center for boring would require a boring fixture.
The operation could be done on a really good mill using a small boring head.
For most of the planet outside turning and common sense prevail as the process of choice.

K&M is the tool I use to turn case necks on my brass. It's a great tool and works even better with a power adapter I have to hold the case rims and turn the brass.

OLD TUCK wrote on Sep 4^th, 2018 at 12:54pm:

No argument from me with what works well for anyone. Did you mean hundreds or thousandths? I believe using tools such as the pictured neck turners along with others, runout is regularly held to the very low few thousandths for loaded rounds. Only thoughts.

I O.D. turn on my lathe.   

Decap, clean, size and expand all your brass so you have uniform I.D. across the lot.   Neck I.D. especially must be clean.

Put a piece of round scrap in the chuck, and turn a "spud" that is .002" larger than the neck I.D.   Length maybe 1" or so.  (For .40 caliber & up make that .003".)  Polish smooth.   

Use a live center in the tailstock to push a case onto the spud.  The brass tension will be plenty enough to drive it.   

Turn the neck with the feed going backwards, i.e. feeding away from the chuck, (assuming your lathe will do that).   

Once you get the cross slide set, lock it.  Run the carriage back by hand until the tool is off the work when it comes time to remove the case from the spud. 

Use a tool with at least 1/16" nose radius - 1/8" is even better.  Keep RPM very low and use a fine feed.  Rake should be zero or a couple of degrees positive.   

Turn only as far as the seating depth you will be using.  Don't want to cut into the body taper of the case. 

Tap the case off the spud using a pair of pliers and a small mallet.  (This doesn't work for rimless cases, but who uses those anymore?)    

Because the spud O.D. is necessarily running true to the spindle axis, the finished neck walls will be very uniform.  Neck wall thickness from case to case will also be uniform, so all your cases will give the same tension.