Both Gulandi 16 wads will work in the 16 2 & 1/2” Cheddite, not as nice as the DR-16, but they are a suitable alternative. BP sells them as does or did Grafs and Precision reloading. Nick Sisley published some time ago in Skeet Shooting magazine loads so for RST/Cheddite, now in Hogdons Reloading, using then PB and 7625 along with International and Universal, using the DR and Gulandi wads. Some of us use 20/28 as well as Green Dot. Good luck.
When I started using the DR16's in the 2 3/4" Herters hulls, I worked up a load and had it tested by ballistician Tom Armbrust using 20/28:
16ga Herters hull
Cheddite 209 primer
17.3 grains 20/28
7/8 oz shot
Avg velocity 1182 fps
Ave pressure 7420 psi
20/28 can be difficult to find these days, but the real problem is the DR16 wads. Something similar might work with some of the wads BP sells.
