In the video above Travis Haley demonstrates a couple carbine handgrip positions and fires splits with each. Watch how wobbly the rifle is with the magwell grip- thats not for me.
Look at the C-Clamp grip illustrated below. The support hand forms a “C” with the thumb on top of the handguard and as far forward as you can safely place it. Now lean into the gun- aggressive stance- you will find that you can get rounds on target faster and keep the muzzle down more effectively. No more wobble!!