1.
If a gun, or a person firing a gun, blasts away, the gun is fired continuously for a period of time.
Suddenly all the men pull out pistols and begin blasting away.
PHRASAL VERB: V P
2.
If something such as a radio or a pop group is blasting away, it is producing a loud noise.
Clock-radios ~ until you get up.
= blare out
PHRASAL VERB: V P