I use 5 gr of TG behind a 240 gr cast SWC.Gives 775 fps in my model 29 with very good accuracy and is my plinking/target load.
As above posters note,be very careful with TG and double charges,you use such a small amount of this powder that you really cant tell with a casual glance whether you have a double charge or not.However my load of 5 grains is half of the max load,so if I ever inadvertantly threw a double charge,I should still be OK!Either way,I would stick to using TG for light target loads,if you want more velocity,use another powder.TG is pretty unforgiving