Barrels of Blasting Jelly, and the zero-mana artifact, adding six ({C} magic symbol) .
Continue activating and resolving the
Barrels of Blasting Jelly ability, causing you to pay ({1} magic symbol) and adding ({1} magic symbol) .
Scrap Trawler triggers four times and
Myr Retriever triggers once.
Resolve the
Scrap Trawler trigger from the 0 cost artifact, returning nothing to your hand.
Resolve the
Scrap Trawler trigger from
Barrels of Blasting Jelly, returning the 0 cost artifact from your graveyard to your hand.
Resolve the
Scrap Trawler trigger from
Myr Retriever, returning
Barrels of Blasting Jelly from your graveyard to your hand.
Resolve the
Scrap Trawler trigger from itself, returning
Myr Retriever from your graveyard to your hand.
Resolve the
Myr Retriever trigger, returning
Scrap Trawler from your graveyard to your hand.
Cast the 0 cost artifact by paying ({0} magic symbol) .
Cast
Barrels of Blasting Jelly by paying ({1} magic symbol) .
Cast
Myr Retriever by paying ({2} magic symbol) .
Cast
Scrap Trawler by paying ({3} magic symbol) .
Repeat.
Notes
This combo works by taking advantage of the fact that you can activate mana abilities during the declared activation of an activated ability. This allows you to delay putting the Trawler and Retriever triggers on the stack (and selecting their targets) until both permanents are in the graveyard. For more information, please see rules 605.3, 602.2b, and 601.2g.