The present paper describes experiments carried out with a 40-mm regenerative liquid-propellant gun at the Ernst-Mach-Institut and lumped parameter representations of the gun performance developed at WDT 91. The test ®xture is equipped with a 2.53 m smooth-bore gun tube and ®res conventional 40-mm projectiles of 0.936 kg mass. It has an initial gun chamber volume of 219 cm 3 and a reservoir of 575 cm 3 . A two-piston system, an in-line annular injector with a ®xed center piston, are used for liquid propellant injection. The differential area ratio is 2 : 1. The pyrotechnic igniter (DM 1101 primer) supported by a priming charge of 6 g black powder combined with 30 cm 3 liquidpropellant containing 80 weight% nitromethane and 20 weight% methanol (type NMaM 80a20) starts piston motion and ignites the injected liquid-propellant jet. Experimental analysis of gun performance is based on pressure measurements in the reservoir and combustion chamber as well as at the muzzle, inductive recordings of injection piston travel, microwave interferometer (5 GHz) measurements of in-bore projectile motion, and inductive measurements of projectile launch velocity. When ®ring the gun with a charge of 550 cm 3 of the liquid propellant type NMaM 70a30, which has a relatively low energy content, then maximum pressures are of the order of 480 MPa in the reservoir, 400 MPa in the combustion cham-ber, and 50 MPa at the muzzle. Pressure oscillations are superimposed to the pressure recordings which, in the combustion chamber, go up to 250 MPa with a leading frequency of 28 kHz. The projectile launch velocity is 950 mas. The lumped parameter modeling represents quite well the measured gun performance. It supports gun design and can be used for parameter studies, if properly adjusted to droplet burning. For example, effects caused by variations in the vent area have been simulated.