Abstract: A hammer drive, powder actuated tool having a main barrel housing, fastener drive and guide means telescopically slidable in one end of the housing and having a muzzle end for orienting a fastener and a breech end for orienting a fastener-driving powder charge, the other end of said main housing having first anvil means thereon, second anvil means including firing pin means, spring means of substantial force biasing said first and second anvil means apart, and movable safety means disposed between the breech end of said fastener drive and guide means and said firing pin means preventing unrestricted axial movement therebetween and contact between said firing pin and powder charge.