The gun was the primary armament of the Czech LT vz. 38 light tank, known in German service as the Panzer 38(t).
The primary user of the A7 was the Wehrmacht during World War II where the weapon went by the name 3,7cm Kampfwagenkanone 38(t).
In German service, in addition to conventional high explosive ammunition, the weapon fired two anti-tank rounds. The primary round was the Panzergranate 39 armor-piercing composite ballistic cap (APCBC) which could penetrate 41 mm of armor plate at 100 m and 35 mm at 500 m. Penetration dropped to 29 mm at 1000 m and 24 mm at 1500 m. The APCBC round was ineffective at 2000 m. The rarer tungsten Panzergranate 40 armor-piercing composite rigid (APCR) round could penetrate 64 mm at 100 m, but only 34 mm at 500 m. The APCR round was not effective at 1000 m or beyond.