I have not seen anyone consistently shoot 5 inches at 1000 yards with a 338lm. But then again, I have never seen anyone do 5 inches at 1000 yards consistently with any caliber.
Here's a plot of two 15-shot groups; both just under 5 inches. .30-.338 Keele with two bullet weights. First fired a 190 then a 200 then a 190 alternately once every 20 to 25 seconds. X-ring's 10 inches.