Some additional informations:
1) Kent Tungsten Matrix 12ga 2 1/2 28 gram loads are same price from Ballistics Products as the Nice Shot loads from RST. Probably not much difference in use.
2) RST claims to be loading "Nice Shot", NOT ecotungsten. I understand ecotungsten to be some variant of HeviShot and not clearly suitable to use in pre 1940 doubles, no matter what the hype says. Nice Shot seems to be some variant of Tungsten Matrix.

Niklas