Well, it depends.
In my .62, it likes about 135 grains of Ffg. My .72 seemed to like 150 grains of Ffg. Both of those were slow twist rifling.
Of course, the best advice is to let the rifle tell you what it wants, rather than you telling the rifle what it is going to like.
Start out at about 1 grain per caliber and work up in 5 grain increments. Tightest group wins.
Have fun with it.
John