Time to re-visit the .400 GNR! A method.

It would not surprise me too much if Remington tried to replicate it with a 400 Bushmaster. Nah, the tolerances are really close on the parent .30-30 aka .32-40 Win. case. They do have a rimless “.400 Legend” that almost copies the .401 Win.

Since the .38-55 is basically that same case tapering to .378”, and Starline makes good controlled thickness brass, we figured that might work. It’s a little long at 2.1” (trim to 1.97”). I tried full length to see if blowing it out would shrink the length. Yes, but not enough, just a tiny bit actually. It does mic at 0.0075”- 0.008” neck thickness, very consistently. The .400 GNR dies do not sport an expander ball. Some steps are probably smart, but I went from .375 straight to .416”. Then back down in the .400 sizer. Virgin brass so no problems. It was the only intermediate dies I had on hand with a useable expander. Blowing out lesser dia. loaded rounds might be best if you can afford to manage that. The bullets don’t go very far and it’s easy on cases. A “blank” on a straight tapered case is not very effective unless you used a dense filler to fireform.

I just used what was in arms reach. It looks like it will work. Necking up slightly, then down to load a useful projectile. I rang steel with my light 4227 load and plain 200 gr. bullet. Not 100% formed, needed more powder, but close enough for the test. Loading these up and plinking to make cases (they are notably powerful though) will be profitable fun.

The first on the left is the original Starline 2.1” .38/55. I expanded a bit of it to .416. I had a little trouble with the Hornady mouth belling die, so I used the LEE universal and loaded a 0.402” bullet. The diameter at the loaded round’s neck is exactly 0.418”, perfect. Next is the fire formed case. It’s about 2.05” here. Lastly is a fire formed case.30-30 that happened to be a useful 0.008” wall thickness at the neck. Most seemed too thick. It’s still a little long, 1.99” as shown, just 0.003” longer than trim spec.