Hemingway wrote about his big double in .577 NE. I think that made the chambering popular in days gone by.

I have always regarded the .577 NE as the largest double rifle loading I would consider acquiring and using for hunting. The weight of a .600 (or larger) puts me off a bit as does the price for most of them.

I am not a collector nor interested in being one (nor can afford to!). In reality does a .600 or .700 add or detract from the effectiveness on close-in dangerous game in the hands of the average client?

Since shooting Marrakai's "Fat Lady" in .577 2 3/4" three years ago (built on a Greener shotgun of suitable frame), I have wanted to emulate a similar double (with longer barrel) and acquired a suitable shotgun. Its still in the gun safe as I have liked it as a shotgun too much, so am looking for a second one at good price!