Lancaster and Nitro John
The rifle does not yet have a bolt, we just yesterday actually got delivery. Steve Bertram is chasing one down to use in the "restoration" to shooting condition.

The ".242" undoubtedly was the expected bore at top of rifling lands while the groove depth was supposedly ~.249". Who knows now, maybe Vickers quality control for bore dimensions was not that good?
As I have sourced an original unfired box of 10 Kynoch .242 Vickers I can say with fair certainty that all the Kynoch .242 Vickers ammo had bullets of .247" diameter.

- Mike