Consider this:
Base diameter of .303" = .458"
Base diameter of 7.62 = .484"
Area of .303" base = .458/2 x 3.14159 = .1647 square inch.
Area of 7,62 base = .484/2 x 3.14159 = .1839 square inch
Ratio therefore is .1839/.1647 = 1.1116 in favour of the 7.62 or 1.112 for short.
Bolt THRUST therefore will be the Ratio of the base areas times the Chamber Pressure, which we already know are in a ratio of (57000/45000=) 1.267.
SO 1.267 x 1.112 = 1.408904 or, for short, 1.409 TIMES the thrust ALREADY on the Lee-Enfield bolt...... which is well known to be springy already.
OR, if you work it from the RIM diameters, you are looking at .530" versus .564. This is because the cartridges are a single piece each and thus exert thrust according to the RIM areas. Here, we get:
.530/2 x 3.14159 = .2206 sq inch versus .564/2 x 3.14159 = .2498 sq inch for a ratio of .2498/.2206 = 1.132
and a Thrust ratio of 1.132 x 1.267 = 1.434 TIMES the thrust normally there.... on a springy bolt.
I certainly wouldn't pull the trigger on it.
Nor would I advise anyone else even to think of it.
.