Oh, don't call this an error. It's just the size of the shells. It does look funny, but has no influence on the game. If you really hate this, delete those lines from the tanks that throw them:
Unit.Gunners.1.Gunner.Shot_Effects.4.Effect.MeshName = cartridge
Unit.Gunners.1.Gunner.Ground_Incidence_Effects = 0
Unit.Gunners.1.Gunner.Water_Incidence_Effects = 1
and change the value of
to 4. Should work.
Unit.Gunners.1.Gunner.Shot_Effects = 5