These are the only loads I've tested, for what it's worth. It's been a few years, so I'm not sure how many rounds per load this covered:

CCI 200, Remington 35W case
Woodleigh 250gn, no crimp, 26" barrels

52 gn IMR 4831 3.36 OAL 2059
53 gn IMR 4831 3.36 OAL 2100
54 gn IMR 4831 3.36 OAL 2153
56 gn IMR 4831 3.30 OAL 2313

To start I gathered 9-10 loading manuals and listed each of their 2300 to 2400 fps 250gn 338-06 and 35 Whelen loads, keeping in mind the lower pressure limit of the 318 vs 30-06 and that the Brits liked to use 28-30" barrels for their quoted numbers. Based on that, and kynoch's "blue sky", I think +-2300 is probably more realistic in 26" barrels.

Bob