Pulse energy scaling of longitudinally excited Sr
+discharge recombination lasers has been investigated for a series of tubes with active volumes of 30, 200, and 1000 cm
3operating at low pulse repetition rates. Specific energy densities (

J/cm
3in the short-pulse mode) and conversion efficiencies (∼ 0.1 percent) were found to remain approximately constant with increasing volume. Single pulse energies exceeding 6 mJ at λ 430.5 nm corresponding to peak powers aver 20 kW have been achieved.