I get this question at least once a month. How to make 400 Whelen brass for my new rifle. It's very easy to do, but if you don't do a couple of important steps, it will fail.
First, make sure you have compatible dies and chamber. All I use is the Griffin and Howe chamber from Manson, and matching dies from CH4D. Since this cartridge has been around so long and has been subject to so much (mis) information, it can be challenging if you don't have compatibility. Many gunsmiths and writers have made this much more confusing than it needed to be.
Brass; I find that most any brass will work, but the only kind I found that does not need annealing is LC Match. It seems to already have been annealed, well. Commercial brass does need annealing. Don't anneal more than .1 inch below the shoulder. Too much annealing will make the brass stick in the chamber. Learning how to anneal brass is another topic. I actually like the hold the case head in your fingers and drop it into a bucket of water method; that prevents too much heat. Mechanical holders do not have a temperature safety stop like fingers do.
You need expander plugs; the pic shows some for the Lee Universal die; one takes the brass from 30 to 40. The second one takes it from 40 to 44, and makes the shoulder .460! This is super important. The C&H chamber has a .458 shoulder and if you do not get your brass above that, you will have issues.
Lube the inside super well, more than at any other time, and work the brass up and down; don't try to horse it up all on one ram.
Then, Fl size as normally and presto; you will have a correct piece of brass which you can proceed to load as usual.
This is for converting 30-06 brass, although 35 Whelen will work well too. Have fun; the 400 Whelen is a lot of power (450-400 Nitro kind of power) in a small package.

Or buy 06 basic brass(when you can find it) and simply size it and trim if needed.

Nope; I am to cheap for that and I have thousands of 30-06!

I've never been an advocate of the method for most cartridge conversions, but have you tried the "Cream of Wheat" method? As I'm sure you know, this consists of charging the case with a modest amount of pistol/shotgun powder then placing a filler like CoW on top of it. Point the gun in the air and shoot. Supposedly, the case shoulders and neck will pop out to the chamber dimensions.

You may have done this. I haven't. Comments?

No this method will definitely not work with the 400 Whelen G&H chamber. The only other method that will work is if you use the "jam a bullet into the throat" method, and fire a medium rifle load out of it.
Reason; the shoulder is too small on 30-06 brass to hold it for firing normally in the G&H chamber.

I have used the C of W method. It works, but like a few other methods if the powder charge is too light you have rounded shoulders and cases that are still tapered! (I used corn starch).

Hip

P.S. Used in .256W (.22 Jet brass) and .257AI (.257R and .244Rem. brass).

I would recommend annealing the case necks of 30-06 brass before necking cases up in a sizing die. I found the expansion from 30 caliber to 35 caliber caused a high percentage of case neck splits.

Then, load the cartridges as normal, grease them up, and fire them. That's what I do.





These were fired in a claw extractor rifle, and the claw kept the base against the bolt face, more or less, but enough that the firing pin strike was enough to ignite the primer. Lubricating the case prevents the case mouth and shoulder from gripping the chamber. So as pressure rises, the case slides to the bolt face, the shoulders fold out, and what you end up with, is a stress free perfectly fire formed case. If the case shoulder or neck grips the front of the chamber, the sidewalls are likely to be stretched, and you end up with case head separations.

I do this when fireforming, basically all my new cases. Particularly belted magnums which are expensive, and the base to shoulder distance is not controlled. To prevent sidewall stretch, first firing, rounds are greased up.

the rifle





the cases,





and the group.

Do you offer those expander's for sale?

The 400 W you built me shoots lights out by the way!!!

Yes, PM me.
Douglas barrels (which is what you have) will shoot with, or exceed, any other make.
Douglas just added 30 reamers to their inventory, for a new total of 193 calibers they chamber for.