http://www.recguns.com/VIIE7.html
The above url leads to a piece on 2 gr. of Bullseye behind a button bullet.
http://members.aol.com/lishsu/longgun.html
The above url sells the 155 gr. 45/70 bullet.
With my very short barreled 45/70, subsonic gas behind bullet is at about 1/2 gr. Bullseye, and I use a .457" soft lead ball, that wieghs about 150 gr.
If you have a supressor, then I guess you don't care about keeping the gas subsonic, that is the surpressor's job.