The key is that the Silan "Government Army" is essentially a paramilitary force, more like an armed police, with its main function being to maintain domestic social order. Since there's no possibility of fighting foreign enemies, it hasn't been equipped with many heavy weapons. Even automatic weapons like machine guns are sparse.
During the outbreak of the civil war, the main weapon of the Silan Government Army was still the Empire-aided BQ-99 rifle.
