I was just making some m3 threads on a 303 part. I used a g76. Im pretty sure this is the code I used:
G76 P031060 Q0010 R.001
G76 X.096 Z1.600 P0110 Q0050 F.01968 R-.002
In my experience when I get torn threads my initial cut has been too deep so try going with a smaller first cut.
Also one thing to look for, if your starting point in X is too close to the major diameter the threading tool wont clear the threads upon rapid retract and it will buzz over the top of the threads which looks like tearing unless you look very closely. So if a smaller initial DOC doesnt help try raising up the start point in X.
I usually do OD threading <.375" at 1000 rpm regardless of size and it always works for me.
Lastly, Ive noticed my threads are a lot nicer if I leave .001-.002 on the major and program a deburr pass to take off a couple thousandths after threading then give the threads another 2 or so passes at minor,
so, turn major .002 over, thread normally, turn major again to final size, thread again at minor dia 2 passes