Jaeger Precision builds a customized airsoft rifle based on the Salvo Precision BRN-180 platform. The process begins with internal modifications, specifically addressing the hop-up system. He modifies the hop arm and installs a Flamingo rubber and a stainless steel barrel to improve accuracy. Some fine-tuning is required, including filing parts of the hop-up unit and the barrel to ensure everything fits and functions correctly without applying excessive pressure.