I have two 870 Police Magnums, a 18.5 and 20 inch. I orginally had a SFIV-s on the 20 inch, which made it roughly the same length as the 18.5 inch weapon with a SFI stock. Shooting with this stock is brutality, especially with the "SWAT" but plate. I have also had trouble with the comb hitting me in the cheek bone, which feels like a punch, only harder. This weapon/stock combo is the only "fighting shotgun" I have ever experienced this with. I elected to use the shorter SFIV-s on my 18.5 inch weapon to maximize manuverability. I put a Speed Feed III magazine stock on my 20 inch 870, since its already too long and making it shorter doesn't make sense anymore. For the majority of aplications, the SpeeFeed III is awesome. I have the ATI pistol grip stock on my 590A1 six shot, which I really like. It doesn't require an adapter and fits much better than it did on any of my Remington's. The adapter really bugged me, but if it doesn't confront you, by all means....Its one of my favorite stocks. Choate also makes a good stock, worth looking at. There is a reason the majority of the guys here, and in LE use the Speed Feed stock. Its the cat's ass.