The Extra power buffer spring by SpinCo is a cutting-edge advancement in AR buffer spring technology, initially developed in 2006 for a Force Modernization Team. It is engineered to enhance the reliability and performance of M4 carbines in challenging conditions, particularly in the Eastern Asia Theatre. The Red spring variant offers a load capacity approximately 25% greater than the White spring, addressing specific load Constants in its design. This increased load capacity ensures superior performance and reliability, especially in high-stress environments. It is ideal for use in various calibers, including 9mm, 6.8 SPC, 6.5 Grendel, .450 Bushmaster, .450 SOCOM, .500 Beowulf and Colt LE6920 carbines. However, individual firearms may vary based on port values and ammunition power factors. For optimal performance, users should consult the provided tuning procedure reference documents to ensure the Extra power buffer spring is perfectly matched to their specific firearm setup, delivering unparalleled reliability and function. The Sprinco USA extra power buffer spring is engineered to resolve reliability issues in M4 carbines, particularly those encountered in the eastern Asia theater The red spring is engineered with design loads approximately 25% greater than those of the white spring, thereby enhancing performance across various calibers, including 9mm 6.8 SPC and .500 Beowulf Prior to use, consult the tuning procedure reference documents, as the optimal spring selection may differ depending on the specific characteristics of the weapon and the ammunition loads