Following up on the earlier BA-I medium armored car also built by Iz, the BA-3 and BA-6 were the next attempt at creating a wheeled reconnaissance vehicle with sufficient firepower to engage enemy tanks. Like their predecessor, they were based on a modified chassis of the Ford AA truck which was itself the basis of the domestically produced GAZ-AAA. The new vehicles features a three-axle 6x4 configuration with an angled hull that was modestly sloped. Armor protection was relatively light, offering protection against small caliber weapons with the BA-6 introducing bulletproof tires which were obtained by adding rubber sponge. The main difference with the BA-I was the increase in caliber of its main weapon, in this case the widely used 45-mm 20-K gun on a turret that was largely borrowed from the T-26 tank. This was a highly effective gun by pre-war and even early war standards and would be the most powerful used on an armored car until the 6-pdr was fitted on the British AEC in 1943. Unfortunately, practice showed that heavily armed armored cars were not able to operate on the front lines effectively given their inferior off-road performance to tracked vehicles as well as weak armor protection. Nevertheless the BA-3/6 saw combat in the Spanish Civil War, the Khalkhin-Gol incident, the Winter War and the early stages of the German invasion, by which time they had been superseded by the BA-10.

A prototype of the BA-3 lacking armored steel was built in April 1933 and first seen on parade on 1 May. An improved version was known as the BA-3M which included the engines of the GAZ-AAA and bulletproof tires. Prototype of the BA-6 was built in 1936 and differed from the BA-3 in having a wider wheel track among other chassis modifications. External modifications included the removal of the rear door and observation windows. The improved BA-6M had thicker armor, a radio station and a GAZ-M1 engine. Prototype rail vehicles were built for both designs but never put into production.