John
Barrel lengths in the RWS tables are 60 cm / 23,6 in for standard calibres and 65 cm / 25,6 cm for magnum ones.
With regards to bullet weights for 7 mm calibres you're right for the theory; for the practice I leave the rifles deciding and I select the bullets type & weight that give the best accuracy result. For my 7x64 Mauser 66 and 7x65R kipplauf, accuracy is best with the KS bullet in 8 grams / 123 grains while for the 7x64 Mannlicher Schoenauer and Dumoulin it is with KS bullet in 10,5 gr / 162 grains.
Louis