Hornady also makes custom dies but I think RCBS has that die in its inventory. Just get a FL die. Any should work. Neil Jones also makes custom dies from your fired brass. They run about $175. I think JLC somewhere in Iowa or Indian can supply modifications to dies, or he may even make them.

I just neck up 7mm mag brass. Wilson also make arbor dies for the 30-338. Neil Jones are either threaded or arbor type and run over $200. You can look at shooter's corner and they might have some used dies. You can send your die to JLC and he will make it like the redding bushing die and his cost is $35. I have two 30-338 one has 1/12 twist the other 1/10 and I use Wilson arbor dies and redding body die when sizing is needed. Great round.

The closest you'll come is 308 Norma Mag brass for preformed. There is nothing wrong with necking down 338 Win Mag brass, or necking up 7mm Rem Mag brass. Either will work fine. It's likely you need a FL die rather than a neck die, but that shouldn't make much difference. I can't envision the bulge you're talking about so anything there is pure speculation on my part.

The brass you have with while using the correct FL die should work just fine and you'll not even realize the necks are sizing down one caliber, but you do have to have the correct die.

The bulge you're talking about is due to improper setup of your neck sizing die. The same thing happens to me with my 300 H&H die if I don't have it setup properly. Re-read the instructions that came with the die. It's a Monday and I don't have time to give you all the details. Worst case, call RCBS and they'll set you straight instantly.

Sinclair sells a neck mandel so opens the neck right up and no need to run in a FL die if using 7mag brass. Glad to see so many 30-338 shooters!

Ditto to the K-fisher's comment. I've reloaded 30-338 for the last couple of years and if there is anything simpler than running the .338 case into the die, I don't know what it is. Ku-dude

I prefer to use the .338win brass over the 7mm bras just cause the headstamp. I know my son will someday be using this rifle and I want to minimize the chance of mistakes with the ammo.