First and fore most the OAL must fit in the mag well with a little to spare.
Then what bullet are you using ? Barnes X type bullet shoot best seated farther off the lands than most bullets.
I seat hunting ammo a little farther off the lands just incase a bullet moves in the mag about 20-25 /1000
varmit ammo I load at as close as 10/1000 off
IMO find a load that shoots good at recomended OAL and then you can start customizing the length longer never shorter.