Bulldog:

Bores that are "nice with no cordite burn or throat erosion" are hard to find in pre-war Nitros these days. Cordite tracks don't hurt anything, but most rifles have them. Sounds nice. Having listened to J. J. 's critique of several pre-war British rifles lately, if he didn't find something to bitch about, it must be pretty good.

Yeah, some variance is normal. Woodleigh .408s should be fine. That's what I use in mine. Standard dies will work fine for either bullet diameter, but you'll need an expander ball that is appropriate for the .408s. My 3 1/4" dies came with one for .411. Personally, I never use an expander with double rifle dies anyway (I never crimp either), but that's too different for most guys to get their heads around. With this cartridge, I would strongly suggest that you not go the elcheapo route with the dies. I'd suggest RCBS. Avoid CH4D.

If the .450 Bell brass is thin rim (.040", keep in mind that Bell also made .060" thick rim .450 basic) then yeah, you can form .450/.400 3 1/4" from it. I don't think I'd go to the trouble without trying the formed Jamison first though. Horneber will be OK, but, barring luck, will be a pain to get.

As for bullets, I use Woodleighs and Hawks. Do your load development with Woodleigh softs until you've got a final load for them. Then reduce a few grains and work back up with solids, until you have a load that puts softs and solids together. After that, you have no need to, and should not, shoot solids except for hunting. Then you can move on to the Hawks for a pig and deer bullet. Don't pull the trigger on a Hawk without reducing the Woodleigh load 10%, then work back up. Hawks can get squirrelly fast in some rifles. Don't shoot handloads without a chronograph until they're finalized.

As for the banded bullets you expressed an interest in....you've spent the money, you need to study it and decide. I understand the theory behind the banded mono designs just fine, and I don't buy it for a nanosecond, nor can I see any need for them whatsoever. I would never fire one in one of my double rifles.
---------------------------------------------------------------------------