The barrel address indicates that the rifle was assembled after the serial would indicates. Using up excess 250 blanks seems the most feasible given that the integral sight base was created prior to boring.
Barrels went from having the small integral featherweight, to long integral featherweight, to long integral medium weight, to raised ramp medium all in about a three year period of time. Seems to be a mix of what was used till old inventory was cleared out.
If yours is a 22" featherweight barrel, then I agree with Rick. It's quite possibly a barrel that was profiled for a 99G in 250-3000 and they were put on 99F's. You need to get an early 99G in 250-3000 and see if the barrels match up.
99F in 303 at 281,675 with 20" barrel
deerstalker has a 99G in 30-30 at 282,4xx with 20" barrel (I think I got SN right)
99F in 22HP at 284,291 with 20" barrel with short integral sight
99F in 22HP at 285,512 with 20" barrel and short integral sight
