My thief player set a bomb and hid with a wizard player who was going to ignite it from afar with magic when the guards got close to it. While they waited the wizard got the bright idea to cast "enlarge" on it and turn 1lb of explosive into 8lb of explosive.
I winged it a bit and went with the explosion being twice as large (hitting everyone in 10 feet instead of 5) and dealing an extra 1d4 damage, though that's supposed to be the effect if it's a weapon.
Under RAW is there proper way to handle an 'enlarged' explosive?
Enlarge says it grows either an object or a creature and makes it 8 times as heavy. The intuitive thing would have been to treat that bomb like it was 8 bombs, as 8 pounds of C4 would be 8 times more powerful than one pound. Though I tried to stick as close to the spell as I could which says attacks with enlarged weapons add an additional 1d4 damage, so I put the damage up by 1d4. As it's size also increases by one size category I reasoned that would mean the bomb's "Each creature within 5 feet" blast size would go up by one size category to 10 feet.