Just so everybody knows, on that spring - and Sprinco makes GREAT springs...
http://www.sprinco.com/tactical.html
"ORANGE Spring" The ONLY specifically engineered EXTRA POWER Buffer Spring for .308 Carbine Platforms using standard 7" Depth M4 extension tubes and .308 short 2.5" buffers (Including aftermarket "heavy buffers.") You cannot clip coils from any other commercially available buffer spring to yield the proper spring loads for this application, especially in heavily gassed .308 carbine platforms. We started from scratch on this design to provide Operators with a viable alternative to existing OEM and aftermarket offerings. Platforms known to exist using this approach include DPMS, Bushmaster (Post 2010), Remington, CMMG, Mega, SA Defense, Colt 901, Rock River Arms and many others. Color Coded ORANGE.
The Sprinco ORANGE spring is specifically designed for the .308AR system, specifically for DPMS-based LR308 recoil systems. That's the AR15 Carbine receiver extension (7" internal depth) and the 2.5" long .308AR Carbine buffer.
Just don't want people with a rifle receiver extension going out and buying this spring, and saying it sucks. It doesn't suck. It excels - for exactly what it was designed to do.
If you buy this spring, and use it on an Armalite AR-10 Carbine system, then just slap yourself. Or,I'll do it for you.