I also found this on one of the US reloading sites. No guarantees!
"Try 6.7 grs. of Bullseye and a 150-gr. RNSP (.30-30 bullet). You may want to bump the charge up 0.2 grs. to make sure the bullet exits the barrel, but this load gives me 1035 fps and 2.5 - 3" groups at 100 yards. I used large pistol primers, but large rifle primers should be OK. A chronograph is a BIG help when loading subsonic rounds."
Midway USA carried Lapua 200 grain Sub Sonic rounds but I wonder what twist you need. Surely a 1-10 would be inadequate. I did quite a bit of experimentation with 30 Whisper and shot 220 grain bullets at 1040 fps but that used a 1-8" twist. The loads were stable to 200M.
~Muir