The rifle bbl on my Miller & Val Greiss 9.3x72R is stamped as follows;
Eagle with crown over G beside it
Eagle
Crown over U
8,8mm/72 (/ =Solid line, showing 8.8mm bore dia atop case length of 72mm)
6,13 (June 1913)
240 (my understanding of this is it would have been the 240th gun proofed in June)
These marks are all between the forend lug & the hinge lug, & are read with breech to you & muzzle pointing away, each on seperate line. Turning muzle to left & rotating toward you, reading left to right just below joint with left shot bbl is
Crown over N followed by K.m.G/12,7gr for the nitro proof of a copper jacketed bullet weighing 12.7 grams (approx 196 grains), no powder charge given.
I can simply see no way the 248 relates to bore dia on a 7MM.