Lands you control can tap to produce at least ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) ({R} magic symbol) .
Steps
Activate all mana-producing lands you control by tapping them, adding at least ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) ({R} magic symbol) .
Cast Turnabout by paying ({U} magic symbol) ({U} magic symbol) , untapping all lands you control.
Cast Mystic Retrieval by paying ({U} magic symbol) , returning Turnabout from your graveyard to your hand.
Cast Mystic Retrieval from your graveyard for its flashback cost by paying ({R} magic symbol) , returning Runic Repetition from your graveyard to your hand and exiling Mystic Retrieval.
Cast Runic Repetition by paying ({U} magic symbol) , returning Mystic Retrieval from exile to your hand.
Repeat.
If lands you control can tap to produce at least ({1} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) ({R} magic symbol) , this combo nets infinite mana.
Results
Infinite magecraft triggers.
Infinite mana permanents you control can produce.
Infinite storm count.
Infinite untap of permanents you control.
Instant/Sorcery with "Return Instant/Sorcery from GY to hand".