On other belted mags, I size the case just enough so that the belt isn't used. Probably everyone here does that.

But with such a long tapering cartridge such as the 375 H&H, there isn't much int he way of a shoulder. Wasnt't the belt designed for the 375 in the first place?

Anyways, how do you adjust your die for this case? I'm just starting to work up loads for this cartridge and it seems the throat is fairly generous in my Brno 602. You can seat the bullets WAY out...

On tghe other hand, it seems to have a low tolerance for pressure. I've only tried RL-15 in it at this point. Others have reported using up to 72gr but I start seeing pressure signs at about 67gr. The Nosler manual lists 68gr as max, by the way...

But back to headspace I'm concerned that FL sizing will work the brass too much for this long tapered cartridge, but I also want to have no problems with feeding/chambering. I'll be using this rifle to hunt grizzlies, so you can imgine I would prefer it if my ammunintion works properly

I always run my hunting ammo through the rifle beforehand, but I want to know 100% that there won't even be a bit of stiffness going into the chamber

I picked up and followed the advice from an older reloading manual that said the 300 H&H and the 375 H&H require full length resizing, which I take as shellholder almost touching the die.
When I started on these cartridges I used a FL die adgusted to resize only the neck and was never able to repeat the the groups I had shot with the first loadings with the new brass. After full length sizeing they both started shooting better. Good Luck, Shayne

Both the 300 & 375 H&H can be FL sized "just right" to fit the chamber just like other cartridges. On the 375 H&H there is plenty of shoulder to headspace on. The 300 H&H will not hold as well.

For dangerous game new brass or at the most once fired brass seems to be the way to go. It's sort of like the "why not" principle of using premium bullets for such game.

The webs on the Remington 375 H&H brass are much heavier than Winchester brass so that's what I am shooting in my 300. Of course the 375 brass gives one the opportunity to set the first shot headspaced on the shouder.

Most moderm reloading dies are made so that they do not touch the belt, even though the remainder of the case is full-length sized.

They are so made because of the dual-headspace (shoulder and belt) problem that occurs with cases that have a distinct shoulder. They are made to ignore the belt so that you can set the correct shoulder-to dimension for that rifle with the dies.

The .375 Howitzer and Howitzer does not have enough shoulder to make partial sizing work well, unless you have a die and chamber combo that is matched that way.

Try your sizer dies and see what you can get away with, it won't hurt.