Home Forums Hunting & Shooting Express Rifles and Big Bores Only Expanding 378Wby to 460Wby

I have quite a few 378 cases, and no 460 and was wondering if this is feasible without annealing? Would I need a tapered expander die?

Just load w/cheap 375 bullets and shoot some-Muddy

boomer68, that's a long way to neck them up to. I can neck 375 Ruger, up to my 416 cal. wildcat in one pass over a .414" Hornady elliptical expander button, but I believe it would take three or four passes over increasing diameter elliptical buttons to go all the way up to .455" Note; most of these Hornady expanders run minus 0.002" from the bullet's diameter.

Then your F.L. sizing die must squeeze the neck back down far enough for the expander to once again expand them back up to the minus 0.002" neck dimension, for your bullet to be seated and stay put.

I would opine that there will have to be some annealing worked into this process, somewhere along the line. Unless you plan on only loading them single shot, the crimps will stress out your case mouths, even more, and start minute cracks forming there.

The good news is that by starting with 378 Wea. cases, you are working over some really good brass. My Hornady 375 Ruger cases, are also some really tough customers. Hornady even anneals their Basic Brass cases. So those which are sold as Basics, are run through a different production line, from their two finished versions of these Ruger cartridge cases.

Even some new production 416 Rigby cases can be loaded up nearly as hot as your Weatherby's. So this is a brass thing, and not merely what's been stamped on their case heads.

I would try to size them up to .416" and then anneal, before going up to the .455" in at least two more steps. Three steps would probably work even better, along with using some of the new super die lubricants, on your expander buttons. You can always run them through your dishwasher, in a cheapie paint filter bag, to clean them out.

If the brass has never been fired you should be able to neck it up w/o annealing. I've turned new 375 H&H brass into 458 lott brass w/ no problems. You should use a tapered expander and use some imperial sizing die wax on the expander. With a tapered expander you can neck up the brass in one pass. If the brass has been fired, I'd definately anneal it before expanding.

The only downside is brass shortens when necked up, so you'll probably find your brass is 0.010-0.020" short.

I guess it comes down to what "laying around" means. If the O.P. had said he had several boxes of virgin 378 Wea. cases laying around, that would be a little different. I've been told that cutting off 416 Wea. belts, makes really tough 416 Rigby cases. And that you can load these up to almost equal the somewhat larger 416 Weatherby cartridge.

Hornady techs told me that 0.050" per step is the absolute max for reforming their 375 Ruger's virgin brass.

Actually I do have a number of boxes of virgin brass. Was thinking of just loading them up as 378 and shooting them out of the 460.

Boomer68, Why not try a few Cream of Wheat blanks first? I use about 20 grs. of DuPont 700, shotgun powder under the cereal. Overworking your brass is still a worry, though. I was reforming some 8mm Mags to my similar 416 Wildcat, and lost about half. But these were junk cases which had already been formed down and fire formed in the 8mm Mag chamber, from R-P 375 H&H virgin parent brass. This was a last resort to get some 8mm Mag sample cases for my reloading die, and forming die, CNC'er. I had necked them down in steps, as these Hornady 375 Ruger Basics were too tough to work down, any other way. The R-P 375 H&H virgin brass was much easier to work over. But half of about half a dozen, said "later", in doing this for a You Tube video.

Your case mouths will probably remain somewhat belled over, but you can deal with those, with your .456 inch expander button. This Cream of Wheat drill doesn't eliminate the need for neck annealing. After two or three firings, my 44 x 356BB cases, start to grow minute cracks right at their case mouths. So far, I've avoided annealing by merely trimming back these same case mouths.

I have necked up and neck down all of the calibres based on the 378.

Best to only change by one calibre at a time otherwise the shoulder will collapse. Calibres like 270 or 30/06 are a different deal because of the sloping shoulder. Calibres like the Ackley Improveds can collapse the shoulder when just seating a bullet unless a bristle brush is put through the neck. Wby stuf is similar.

The problem is amplified if the inside of the neck has cold hard fouling, in other words the reloading or necking is done quite some time after the case was fired but the bristle brush solves the issue.

Hi Mike,

So it would be best to neck up to .416 then .458?

I tried necking up to 0.510" using 460 W brass. It didn't work. I had to anneal first.

That is what I have done.

Just make sure you run a brush through the necks.

I just use the full length dies as I had them in every one of the 378 based calibres.