Re: Whats the longest shot you would take on a brown bear
Sorry about that, blew right by me. Bottom line for me is that I do not know diddly about your .338 cartridge but I expect it would do a fine job. I mentioned that the guide is thinking .338 Lapua or .50BMG, those are the biggest cartridges he knows of. He is confident that either cartridge, particularly the .50 will do the job.
As for comparing a hot .338 with a 300 grain bullet vs a 350 A-Frame out of my .416 Rigby, all I know is that the RIgby did a heck of a job the one time I fired it at a big bear. After that experience for some weird reason I have no interest in a fast bullet, I want a slammer. I have no doubt that your .338 cartridge will do a fine job - a lot of guys hunt bears with much smaller cartridges than the .338 or .416 with confidence.
At one point I thought that blasting a big bear from several hundred yards makes sense - after my trip that interest went away. Good luck with your plans to hunt a big bear with your rifle, no doubt it will work great.