I have a bad habit of grabbing the front of the magwell with my non-firing hand, which is obviously terrible for stability. To remedy this, i put a verticle foregrip on my rifle, to give my hand a more natural place to grip, while extending out my arm further forward for added stability. As others have said, if you just grab the verticle grip, it just makes stability worse than it was before. Thats why when you use one, about 90% of your hand is firmly holding the handguard, while the pinky and ring finger push the grip back into your shoulder. Same theory used in the concept of the afg.