Case Neck Tuning Device

[Dave_C]

In trying to understand case neck turning!

I talk with many shooters who turn case necks and it seems the agreed upon way to do it is to turn the case necks to uniform thickness then resize the brass. I suppose the reason for resizing the brass after turning is to maintain concentricity of the case neck with the forming die.

I've shot enough precision shooting to realize that without turning case necks you are not going to get consitant shot to shot performance. I would imagine that a book could be written on that subject by itself.

What I am intersted in is some feedback from anyone who does precision loading and shooting.

What I am proposing is to develop a tool that I can use in my mill to turn case necks. The actual cutting device can be bought from many sources and this part simply clamps in the milling vise and is perfectly centered under the spindle.

Then a simple collet to grasp the base of the brass, as perfectly centered as possible, and then I can turn my spindle by hand or under power to trim the necks. I most likely will turn it by hand since my mill is belt driven and the slowest speed is 240 RPM. It is very easy to turn by hand due to the large step pully on top.

Now the question: Would a person get a truer neck turning before sizing or after?

Dave C.

[pacrat]

IMO, the answer would depend on the type of die used for sizing.

Using a Lee collet neck sizing die. It would IMO be truer to the axis of the case after sizing. Due to the mechanics of the die the sizing/squeezing is done to a precision ground mandrel down the CL of the case.

All other sizing dies, even expensive neck sizing only dies with changable bushings use friction to swage inside and out to size the neck. The last part of the die to touch the case is the expander button after outside of neck is swaged to just undersize. So neck concentricity is totally dependant on the expander and how squarely it contacts the case at the neck/shoulder juncture inside case and the the thickness of the neck before sizing.

IMO, Lee collet dies, AFTER..........others, slight edge accuracy wise, BEFORE, but use a spud on the cutter that snugly fits neck interior.

Further thoughts and again JM2c.

Often overlooked is the lowly expander button and its function in making accurate ammo with regular friction dies. One thousandths of an inch maximum is optimum press fit for the bullet/neck. Less is better if it holds the bullet OK. If an expander button is less than .001" of the bullet dia. Then the bullet is acting as the expander during the seating operation, and not the button in the sizing die and neck can be tweeked.

[Dave_C]

Pacrat,

What you wrote makes perfect sense in the way my brain understands the process!

I think I will look into the Lee Collet setup.

I did figure out one thing though, I reversed my thought on the setup and put the holder in the vise and will spin the case neck trimmer with the proper mandrel installed.

That way, I can also use this setup to trim to length. Almost have that setup built!

Later,

Dave C.

[jim35010]

I was shooting 1000 yard competition. I have a rifle 6.5 X 284 smithed by Lenord Baity. You turn the brass because the chamber is reamed so close the brass you get won't fit!
If you buy a precision turning tool it will have a mandrel that goes to the inside of the case reaming it to size and an adjustment on the outside that turns the case. you can use an attachment that goes on the rim of the case(shell holder) and tightens with friction then put it in a small drill, if you don't want to turn by hand, but it comes with a shell holder mounted on a handle. All parts are made from carbide and accurate.
You can go to Brenchrest Central and look at some of the vendors.
I use a K&M and I think it is the best for me.
Jim

[Dave_C]

Jim,

Thanks for the reply. I see lots of comments about the Mandrel diameter. Some say you need their expander ball in order to match the case turning mandrel. Lots of complaints about cases not fitting the mandrels after the case was sized.

I do understand the "cases not fitting" the match chamber issue. The whole idea of a match chamber is to get tolerances as close and consistant as possible. Most factory chambers are two large for my tast. I suppose they have to be to accept all brands of brass and different case neck thicknesses.

I'm striving to achieve optimum bullet/bore consistancy with less than .001" run out max! I won't get there until I true up my case necks I'm told. (I think I knew that allready)

I always try to find the person who has allready done it and find out how and why they did what they did. That is how I've learned most of what I know.

Now if I could just remember some of it!

Dave C.

[Dave_C]

I finished up the case length tooling.

This was falling off a log simple: I just took my Lyman (orange) case trimmer apart and used the shell holder and the cutter head.

All I had to do was square up a 4" long 1/2" aluminum anodized plate scap, put a 9/16" hole in the middle with a chamfer to match the shank of the Lyman shell holder head and add a stop so it would not unscrew to far.

Then I made a spindle out of 5/8" Oil hard rod, bored a 25/64ths hole for a 7/16-20 thread to match the cutter head and that was all there was to it.

I made no alterations to the Lyman case trimmer that can not be reasembled if I need it at some point.

So now I set my mechanical stop on the mill so the the arm only comes down to the half position. Then I adjust the table for case length using the .001" dial. Put it on low speed and trim away!

Sure beats turning the crank by hand.

Dave C.

[pacrat]

Sure beats turning the crank by hand.

I have 2 Forester case trimmers. Got I for cheap long ago from E-barf, other was for free, same time frame. 1 is set up as trimmer. Other is set up as neck turner. Both solidly mounted to 3/4 x 4 x 14" piece of oak and can be clamped to bench top in seconds. They are mounted on opposite ends of board. Removed the little thumb and forefinger killing turny handles and in seconds my cordless drill with keyless chuck is power drive.

To speed set-up time and remove doubt. I keep 1 case for each caliber I load for trimmed to minimum lenght permanently labeled and used as set-up stop for the trimmer.


just sharing shortcuts

[Dave_C]

I looked into the Lee Collet neck forming die. The issue I see with it has to do with how the collet works. It is compressed whent he case is forced up. It may work fine but I'm working on a new design that draws the collet up!

I'll forward my work to one of the major manufacureres if I can perfect the idea. Or maybe let them perfedt it, LOL.

Basic design is this. Case can be a fired case or a new case as the die can be made in either version.

If it is a fired case, raise the ram, tighten the die until it sets on your case shoulder. The neck is untouch at this point.

The top assembly drops in or maybe srews in, (not sure yet) it has a mandrel that will fit through the fired case neck. The mandrel is sized say for a .308 bullet, at .3075. The trick is, the mandrel is perfectly concentric to the fired cases outer shell but the untrim outer edeges are not!

So drop in or screw in the top assembly, pull the collet operating lever that pulls up on the collet like a mill would on an R-8 collet and form the case tot he madrel.

Now you can turn the cases outer neck area to whatever you want and everything should be in perfect alignment.

The proceedure is has an extra step if it is a new unfired case as the mandrel will not fit in the case mouth.

Most standard dies simple let the bullet form the case as it is inserted. Bench rest shooter want neck tension to be light and consistant. Drawing the neck down to a mandrel produces a more consistant neck tension and if I can make this thing, should produce a internal case neck perfectly concentric to the case body.

We will see. I worked on the drawings last night. I have arough draft.

I also know that I can not make a working prototype as tolerances will have to be held to .0001" if it is going to work right.

Dave C.

[pacrat]

I looked into the Lee Collet neck forming die. The issue I see with it has to do with how the collet works. It is compressed whent he case is forced up.

Look again. Upward case pressure does not actuate the collet.

The collet is integral top part of a sleeve that extends below the body of the die. It is actuated when the bottom of the sleeve portion of the collet is forced upwards by the shell holder against a floating tapered part in the top of the die that also retains the mandrel. The only force applied to the case is by the collet at the neck and perpendicular to the case.

[Dave_C]

Pacrat,

Well that is what happens when you don't have one in hand to look at. I was trying to see how it worked from Lee's instruction page.

Still, it appears (can't be sure) that the case neck has to slide in the collet while the bottom section closes the collet as it goes upward. Maybe not if the collet, case and closer shell all move together. IF that is how it works, then it should be an awesome die. May have to get one and try it!

Anyway, I sent my design to RCBS Friday and we'll see if they have any interest in it.

Most of the things I try to invent have been done because I had no idea it could not be done that way. LOL

Dave C.

[pacrat]

if the collet, case and closer shell all move together. IF that is how it works, then it should be an awesome die.

That is how it works. Very simple in design and operation. I just don't seem to have the words to properly describe it.

7/8 x 14 hreaded die body and a threaded cap on top to hold the goodies in. Goodies number 3 parts. Goodies consist of the "closer" tapered inside to act on the collet and also hold the "mandrel". Both these parts float in die body until pressured by sleeve/collet which also floats until acted upon by the standard shell holder of the press ram.

I'll see if I can get some pics and post em.

[pacrat]

Lee collet die pic 2 shows sleeve/collet extending below die body. It, the mandrel, and the closer float in the die body until shell holder with case inside is raised by ram. Case slides inside sleeve and shell holder forces sleeve up into closer.