The Extra Power buffer spring, developed by SpinCo in 2006, was originally designed to address M4 carbine reliability issues in the Eastern Asia Theatre for a Force Modernization Team. This Red spring offers a 25% higher load capacity compared to the White spring, making it ideal for specific operational challenges. It's commonly used in firearms chambered in 9mm, 6.8 SPC, 6.5 Grendel, .450 BM, .450 SOCOM, .500 Beowulf and Colt LE6920 carbines. However, individual firearms may exhibit variations depending on their port values and the power factor of the ammunition being used. For best performance, please refer to the provided tuning procedure reference documents before making any usage decisions. The red Extra Power buffer spring is engineered to improve the reliability of the M4 carbine, particularly for operations in eastern Asia The load capacity is 25% greater than that of the white spring, rendering it suitable for a range of calibers, including 9mm 6.8 SPC, among others Prior to use, consult the tuning procedure documentation Be aware that performance may vary depending on the specific gun models and ammunition loads