Help with .308 FL die selection

[Marlin Junky]

I've decided to have Pacific Tool and Gauge cut a custom reamer for me and was wondering who's .308 Winchester FL die would be best for creating a long neck version of the .308W from 8x57 brass. Basically, I'd like to put a near 30-30 length neck on a .308W body. Are there any not so obvious pitfalls I need to look out for?

Thanks for your help,
MJ

[Mk42gunner]

I just sacrificed a .30-06 case in a quest for knowledge, ( I didn't have an 8x57 case handy). With a well lubed case, my RCBS full length sizer set the shoulder back and created a neck that is about .760" long; there is a thickening where the new neck is formed from the case body, it shouldn't be as noticable when using 57mm cases.

Robert

[mpmarty]

When cost is no object (rare) I like Redding dies. They seem to be finished better and hold tolerances more precisely. Otherwise, LEE gets the nod as being cheap and easy to find.

[243winxb]

there is a thickening where the new neck is formed from the case body Its called a donut. Its not a problem unless you seat the bullet deep into the neck shoulder junction area contacting the dounut. This thickness is removed by inside neck reaming and/or outside neck turning. The donut can return after a few firings.
Advanced Case Forming Operations

It has become increasingly popular to form new wildcat cartridges by shortening the parent case and moving the shoulder position back. There are potential problems to consider when performing this type case forming operation to ensure that the cartridges you produce are safe and reliable.

Neck Wall Thickness

The first consideration, is the thickness of the newly formed case necks. When a case neck is reduced in diameter, or moved during case forming, the wall thickness increases. Brass cartridge cases are progressively thicker as you approach the base. This means that when a new case neck is formed from what was previously the parent case's shoulder or body, the neck wall thickness will increase. This can create a dangerous condition if there is not adequate clearance between the neck of the loaded cartridge and the chamber. This clearance can be determined by comparing the measurements of a dummy loaded cartridge and the neck diameter of your chamber. We recommend a minimum clearance of 0.003". If you do not know the neck diameter of your chamber, you should enlist the aid of a competent gunsmith to assist with the project. He will undoubtedly take a chamber cast.

The "Donut"

The second consideration is the formation of a "donut". This is a ring of thicker brass inside the neck of the newly formed case. The donut appears when the neck-shoulder junction of the newly formed case ends up closer to the base than the parent cartridge. This donut must be removed or dangerous pressures will result due to the lack of clearance for the case neck to release the bullet. Again, we recommend a minimum clearance of 0.003".

Neck Thinning

There are two common methods used to reduce the neck wall thickness of cases and remove donuts from their necks. The simplest is neck reaming. Reaming can be performed on a case trimmer or in a special reaming die. The die method is preferred, as the reamer tends to follow the off-center hole in the case neck when reaming on a trimmer.

The preferred method of thinning case necks is to use an outside neck turning tool to remove brass from the outside of the case neck. If the neck turning operation is performed one or two calibers larger than the final desired caliber and a size button is pulled through the neck, it will also remove the donut from the case neck. Neck turning produces a more uniform and concentric case neck than the previously mentioned method of reducing neck wall thickness, reaming.

Some cartridges may require fireforming to produce their final shape before neck turning or reaming can be performed properly. The only safe method we can recommend for this operation, is fireforming cases with an inert filler. For detailed instructions on this method of fireforming cases, see Ken Howell's Designing and Forming Custom Cartridges for Rifles and Handguns.

If you have further questions, please feel free to contact our tech line below.




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[Marlin Junky]

I found an old Bonanza .308 FL die (from the 70's I think) and discovered that an already fire-formed 8mm case run into the .308 die to set the shoulder back creates a ring around the outside of the new neck where the old neck/shoulder junction was. A virgin 8mm case creates a much nicer .308 long neck but it's obvious inside neck reaming will be needed after fire-forming in the new chamber.

MJ

[StarMetal]

Outside neck turning, in my opinion, is easier and better. If you already have a Forster trimmer you can buy the outside neck turning attachment. Works great if you can figure out the instructions.

[Marlin Junky]

Outside neck turning, in my opinion, is easier and better. If you already have a Forster trimmer you can buy the outside neck turning attachment. Works great if you can figure out the instructions.

StarMetal,

I've done a lot of outside neck turning with my Forester trimmer but since the cutter is round, getting all the way down to the bottom of the neck without cutting into the shoulder is impossible. After reloading a case prepared with the Forester outside neck turner a couple times, it's apparent there's a ring inside the case at the neck/shoulder junction which can be felt with the long trimmer pilot.

MJ

[nicholst55]

If you're really worried about the donut, you need a K&M neck turner with this pilot/donut cutter:
http://www.precisionreloading.com/mm5/merchant.mvc?Screen=PROD&Store_Code=PRE&Product_Code=KMCAP30&Category_Code=NECK_TRN_KM

Their standard steel pilot doesn't remove the donut - you need the carbide pilot.

[HangFireW8]

If you're really worried about the donut, you need a K&M neck turner with this pilot/donut cutter:
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Their standard steel pilot doesn't remove the donut - you need the carbide pilot.

*ahem* There is more than one way to skin a cat.

I have removed many a donut (verified with a tubing micrometer) without using either a K&M product or a carbide reamer. I have owned several brands of carbide neck reamers, and sold them all off.

If a pilot (even a non-carbide steel pilot) fits closely enough, and extends far enough inside the neck past the donut, then the excess donut area brass will be proud and a neck turner will take it off.

Many neck turning systems use mouth buttons and are happy to sell you a very expensive carbide neck turner when all you really need is a fitted steel pilot and then the neck turning cutter will do the work.

In a way, what you said is true- Their standard steel pilot doesn't remove the donut. Pilots don't have cutters to remove anything.

After extensive trials, I gave up on neck reamers because they require very precise lathes and very tight holding jaws to ensure they cut on-center. In other words, hand neck turning tools (like the Sinclair and the K&M) and hand-cranked tools (Forster, RCBS) simply cannot hold a case and reamer correctly enough to ensure a centered cut. This was verified after many hundreds of cases were ruined and many, many phone calls were made to tech support numbers.

In the end the simple, easy, and correct thing to do to get rid of donuts is to size the neck to fit a full-neck-length pilot closely, and then use a good hand neck turner (like the Sinclair or K&M) to cut the neck from the outside. The result is uniform neck thickness, unlike the results of the neck reamers.

Anyone trying to tell you that reamers are a superior system for neck wall uniformity has a lot of reamers to sell you.

-HF

[243winxb]

The best way is to inside neck ream first, but leave a little of the extra metal there. Then FLRS using the expander. This moves the donut to the outside. Make 1 or 2 passes with the outside neck turner. I use a Lyman, much like the Forester outside turner. The only way to turn all the way to the shoulder with a Lyman, is FLRS the case first.