Green’s Dictionary of Slang

1. a safe-blower [SE blast].

1914		Wash. Post 11 Nov. Misc. 3/5: The boxman has a string of monachers such as ‘peterman,’ ‘yeggman,’ ‘blaster,’ ‘heavyman’ and ‘soup man.’.
1933		Ersine Und. and Prison Sl.

2. a thug or gangster who is armed [blast v.¹ (3a)].

1935		A.J. Pollock Und. Speaks n.p.: Blaster, a gun-man.
1949		W.R. Burnett Asphalt Jungle in Four Novels (1984) 149: A blaster. Heat-packer. Gunman.
1960, 1975		Wentworth & Flexner DAS.

3. a pistol, a revolver, a shotgun [blast v.¹ (3a)].

1949		Monteleone Criminal Sl. (rev. edn).
1963		M. Spillane Return of the Hood 41: They knew I had a blaster in my belt and would chop them down the second they moved.
1972		D. Pendleton Boston Blitz (1974) 73: The extension phone in one hand, that big silver blaster in the other.
1988		D. Woodrell Muscle for the Wing 198: With just one pull on the twin-triggered blaster he shredded them in tandem.