In this investigation, a high-consistency rubber (HCR) was mixed with five different, typically used crosslinking agents that are based on organic peroxide. Furthermore, the amount of crosslinking agent was varied in order to quantify the effect on the mechanical properties. All materials were processed in a hot pressing process, and, subsequently, post-cured. The properties were characterized by the measurement of the swelling ratio, shore A-hardness, rebound resilience and tensile test. We successfully proved that the swelling ratio is a suitable indicator for the evaluation of the crosslinking density of silicone rubber. The results show that the crosslinking density increases as the amount of crosslinking agent increases. The hardness, rebound resilience, and stress at 100% elongation increase as the crosslinking agent does. In contrast, the ultimate elongation decreases as the crosslinking density rises. The absolute values depend on the type of crosslinking agent used. The most commonly used crosslinking agent for high-consistency rubber is Di(2.4-dichlorobenzoyl) peroxide. We were able to verify that there are more possible curing agents based on organic peroxides on the market. Depending on the required properties, customized silicone elastomers could be easily produced.