Quietest carbine buffer spring i've used - Aero Precision AR15 Carbine Recoil Buffer Spring

Over the past few years, I've built over close to a dozen ARs. I've used a handful of different buffer springs including flat wire varieties, and have one lower set up with a captured spring system. This buffer spring produced the quietest cycling as far as the "sproing" is concerned of all the "normal" springs, and rivals the captured spring buffer system for the quietest. This came as a surprise, as it was quieter than a flat wire buffer spring, which I had read many testimonials promoting.

The OD and ID of the spring (not the wire) seem to be slightly less than standard. They take a little more force to seat the buffer in the spring, but the spring grips the buffer firmly. It also seems to make less contact with the inside of the buffer tube because of this reduced diameter.