Works great for ar-9 builds - Kaw Valley Precision Stainless Steel Heavy Tungsten Buffer

I purchased this buffer after a lot of research into building/tuning a 9mm AR-platform pistol/carbine. Since they operate on direct blowback, it is important to adjust your total reciprocating mass to reduce felt recoil, ensure proper cycling, prevent undue wear on the system, and (most importantly) delay blowback long enough for pressure in the system to drop to safe levels. As such, I was specifically looking for an extended (~4 inch) buffer with internal sliding weights, and the KVP-10oz meets both criteria.

The specific buffer I received weighed in at 10.25 oz which, combined with my 14.4 oz BCG, places it in the approximate "sweet spot" range for 9mm. Though the buffer is actually about 4-1/8" long, it still seemed to cycle properly and I had no FTFs, FTEs, issues with the last round bolt hold open (LRBHO), or any other malfunctions after testing in my build. The recoil was significantly less noticeable compared to when I was originally using a 5.4 oz buffer during my initial build/testing.

All in all, I am very satisfied with the purchase and would recommend it to anybody else building an AR-9.