Most of the guns used in the first and second generation tanks after the war were not very big, and they were basically100 mm/105 mm/15 mm. At this time, although the tank shells were not light, they were still affordable by manpower.

With the increase of gun caliber, when the caliber of 120mm/ 125mm appears, manual loading is a great test for the firing rate and the physical strength of the loader. Studies have shown that when the caliber exceeds 120mm, manual loading is already overwhelmed. So 120mm is a watershed. Western 120mm caliber tank guns are basically filled manually, which is based on this. Soviet Union/Russia developed automatic loading equipment to solve this problem after adopting 125mm caliber.

However, with the passage of time, western tanks also began to adopt automatic loading equipment, such as French leclerc and Japanese Type 90.

The application of automatic loading equipment has brought benefits such as increasing firing rate (6- 10 rounds/minute) and reducing personnel (4 →3), but it has also brought some problems, such as the lack of compartment design (Soviet Union), which led to the decline of survivability and the reduction of ammunition reserve of automatic loading machine magazine (leclerc /90 type).