Re: .338 L/M brass burning through
I don't load for 338LM as I am trying to decide whether to go with 338LM or 338RUM to build out my Wby Mark V. Maybe 300RUM, hmmm 208 A-Max at 3250fps
but I digress...
IMHO
Discard that lot of cases, they are now dangerous.
If you are FL sizing each firing, stop and get a neck sizing die. I am now migrating to Lee collet as it works the brass less.
If you are neck sizing, you might have your die to low. Use a sharpie mark the neck and only size down as far as you need to. IMHO a couple thou of unsized neck to ensure you don't crush the case or bump it with a neck sizing die (ask me how I know) creating excessive head space.
As has been mentioned above, when you do FL size, bump the minimum amount. When I FL size, I anneal first so that I'm working the shoulder brass and not pushing the work hardening all the way down to the webbing.
and last
I really believe that all the 4350's are too fast for a 338 LM unless you are throwing Barnes 160 or 185 only. H4381, rl 22 or 25, IMR7828, H1000, or anything slower than IMR7828.
What I do: I lave limited experience but I prefer to find the powder that covers the largest range of projectile weights for my chambering that also pushes the projectiles pretty fast with the lowest pressure.
Using your caliber, (I favor Olin products) I would choose IMR7828 because it is listed for everything from Barnes 165gns to Sierra 300gns MKs, doesn't top the speed charts for the heavy weights but most important does not top the pressures. H-1000 or H-4381 would be a close second.
Be safe and have fun