I'm at 6 life, not 5, and with 5 cards in hand, not 6. :D
Untap, Upkeep, Draw, Plains (crossing fingers), tap out to play Brightflame for 5, targeting your Oathsworn Giant.
Response?
Ransac: 6
Hand: 4
In Play:
(T) Island
(T) Mountain
(T) Boros Garrison (T: add R/W to mana pool)
(T) Swamp...