I had one in .33 calibre and yes, 9 grains of Swiss 1, .330 swaged LRB and a 3/4" x 012" Patch. I used a Greathead .32 Cal Loading rod as my go-to wooden loading rod was too thick. As I recall it was VERY accurate. My best was 96/100. It was in a MLAGB competition so I don't have the target sadly.
I tried 8.5 grains but I was told they have a counter-bored breech which is designed for 9 grains, mine came without original paperwork so I can't confirm this however. I sold it because I prefer Underhammers.