Polska,
I built a very nice 416 Remington Magnum off an M70. I chopped it down and made it fairly light along the lines of Phil Shoemaker's light rifle. The barrel has a 375H&H contour and it has a lightweight stock, so it turned out very light for a 416. The balance is perfect and there is nothing sluggish in its handling. Using bread and butter Reloader 15 handloads, it works well on about anything you'd shoot with such cartridge. The rifle is well fit, and to me, the recoil is not too much over a stiff 375H&H.
I don't think I'd ever get rid of this rifle due to the work involved to get it where I wanted. But, if I felt the need to get another 416, I'd probably just grab an out of the box 416Ruger and be happy. I think I read a quote from Shoemaker where he wrote that there were probably more 416Rugers sold in the last couple years than all Rigbys sold in the last 100 years. Looking at sales figures, I tend to agree. With such a readily available rifle, you'd probably never have any issue obtaining ammo and/or reloads for many years to come. I've even read where Hornady is on a full court press to have their 375 and 416Ruger ammo readily available within Africa.
Reference needing stainless, I don't think that would give you a free ride if your rifle spends a lot of time in the bottom of a boat while exposed to salt water. No matter what you get, it'll probably end up ugly over the long haul being hosed down with spray paint and/or coated with some sort of teflon or black t, etc. I'd not let chrome moly become a deal breaker. Some of the stainless steels used can degrade pretty quick when continually exposed to salt water.
In reality though, outside professional use or maybe for someone who routinely kills the current "big 5", there is probably zero need for any of those cartridges for a hunting rifle used otherwise. For someone who is a mere short term visitor in a far away land, where the responsibilities of stopping game under an emergency situation falls squarely on the shoulders of an experienced professional guide; I'd worry more about doing your part as a hunter by placing an accurate shot with a recommended cartridge, and I'd leave the professional with the stopping rifle.
Best:)
You confirmed my thoughts, thanks bro... nice to see some other people with common sense in this world haha. Your right, i'll leave the stopping to my partners or the guide. But i'm sure a .416 ruger is plenty to stop anything on the planet... some guys says the bullet is smaller, but that made actually be better because although it doesn't leave as big a hole as a .458 or a 50 caliber rifle, it can penetrate deeper which levels it out
