If your Savage 340 is the same as mine...
Then you've got all of one (1) locking lug, just like the earlier Krag-Jorgensen rifle. From my Speer manual, the .30-30 Winchester generates 38,000 c.u.p. of pressure. The .307 Winchester, a rimmed variant of the .308 Winchester, generates 52,000 c.u.p. of pressure. Wanna trust that to just one locking lug?