With the Carbine Buffers we have-

Construction and Approximate Weights of Carbine Buffers
Standard Carbine- 3.0 oz. Three Steel Weights
H Buffer- 3.8 oz. One Tungsten and Two Steel Weights,
H2 Buffer- 4.6 oz. Two Tungsten and One Steel Weights
H3 Buffer- 5.5 oz. Three Tungsten Weights

Compared to the Rifle Buffer-
Rifle Buffer- 5 oz. Five Steel Weights and One Steel Spacer

If the Rifle Buffer weighed about 5 oz, how did they end up with a Carbine Buffer weighing only 3 oz? Why didn't they start off with a weight approximating the 5.0 oz of the Rifle Buffer? Is it because they didn't think to use tungsten?