I just bought my 590 a - boc - bayonet, its fit was very sloppy. I rectified this by taking my dremel tool with a small grinding stone, I ground out the factory peanning.I then filed the shoulder cuts down a little over an eighth ,tacked it and cleaned up said tack. Repainted butt cap with flat black touch up paint..... ta da perfect fit. The sweetheart looks at me like I'm crazy because because ups just droped it on the porch...... Crazy Cool .... my Mossy is shaping up
