Standard AR15/M4 buffer springs (aka "action springs") are wear items which must be replaced regularly in order for AR-15s to operate reliably, with conservative replacement taking place every 5000 rounds. Sprinco action springs in comparison, are over engineered and will last over 500,000 cycles.
I was first clued in to these springs by former US Marine and US Army Special Forces solider and trainer Mike Pannone, and have run one spring on my main rifle since 2008. Despite a strong dry firing and live fire firing schedule (10-15K annually) this spring is still going strong! We at Weapon Outfitters fully endorse the Sprinco spring's performance and longevity.
There are 5 versions of the spring available
Extra Power (color coded RED): The option with the most spring tension, this spring is suited for rifles and carbines with excessive bolt speeds. This spring is suitable for 14.5"/16" uppers with carbine length gas systems (which are typically over gassed), all suppressed rifles, piston operated rifles, and 9mm conversions.
Medium "enhanced" power (color coded BLUE): A slight increase in spring power makes this spring suited for rack grade weaponry with normal operation parameters. 16" rifles with midlength gas systems, short barreled rifles with carbine length gas systems, etc.
Standard "regular" power (color coded WHITE): Equivalent spring power of a "fresh" AR15/M4 carbine action spring, this spring is for users who do not want to dabble with improving performance with extra power springs, but do not want to frequently replace their action springs as well.
Rifle Length (color coded GREEN): In addition to use in 5.56 Fixed Stock Rifles, the "Green Spring" is just the ticket for use in the VLTOR A-5 Stock System using their standard weight (5.2 Oz.) buffer for maximum versatility with almost any 5.56 upper BBL configuration, both with or without a “can”.
308 Carbine (DPMS/SR-25 Pattern) extra power (color coded ORANGE): This spring is for 308 carbines using the DPMS/KAC SR-25/LMT MWS and Mega MA-Ten pattern.