I have the Spikes ST-T2 buffer. Weights about 4.5 oz. and is Tungsten powder filled. I'm still using the standard buffer spring that came with the Sport.

With the old buffer my casings were ejecting about 10 ft. at about a 45 degree angle (right and rear). With the ST-T2 buffer they travel about 3 ft. with less recoil. I like it.