I have not, but Boddington has. He states (Safari Rifles, p. 44):
"- - - I chronographed several batches of old Kynoch ammo, and the velocities I got weren't even close - the 250-grain loads didn't come up to 2,200 fps. One has to wonder if that was because the ammo was half a century old, or if it ever reached published velocities."

According to Boddington, the factory figure was 2,400 fps.
Kynamco still quotes the same figure of 2,400 fps - in a 28" barrel! Kynamco site
I seem to recollect that WR often fitted their bolt-action rifles with quite unnecessarily long barrels which would explain this. But, really - 28"? C'mon!