What does the 4:1 ratio in M249 combat mix refer to?

The 4:1 ratio in the M249 combat mix specifically refers to the proportion of tracer ammunition to ball ammunition that is used in operational settings. In this context, it indicates that for every four rounds of ball ammunition, one round of tracer ammunition is included. The use of tracer rounds serves a crucial purpose, as they allow the shooter to visually track their shots in flight, enabling better adjustments for aim and fire corrections. This ratio is standardized to enhance effectiveness in combat situations by providing both suppressive fire and an ability to see where rounds are impacting. The configuration of this mix supports the tactical needs of the mission while ensuring the ammunition is used efficiently.