The original M870 Police models used in the USA for many decades were standard 5 round models with wooden furniture. Not until the late 1980's the synthetic furniture models were introduced.

The M870 MK 1, MK 3 and MK 6 are early military models adopted in the 1960's. The Mk 1 has a magazine extension and bayonet lug. The Mk 3 is similar to the Mk 1 but has no bayonet lug. The Mk 6 is an air force model with 4 round magazine. All versions feature wooden furniture and feature an oil finish that differs from the civilian models.

Late production M870P's are also available with a shorter 14 inch barrel. The short barrel models are often referred to as the M870P Entry, although this is not an official name. Most short models feature a pistol grip and many of the accessories found on the full size models are also available.

The current production models of the M870 Police feature a synthetic furniture. The original M870P with synthetic furniture was known as the M870 Police Special or M870PS. Currently the synthetic models are simply referred to as M870P, despite the differences with the original model. The current police models are available in many configurations and may feature a pistol grip, tactical light, magazine extension, ghost ring sights, accessory rails, speedfeed stock or a retractable stock. The latest model is the the M870P MAX and contains many features previously found only on the Scattergun Technology models.

The Police Breacher System is a highly modified M870 designed for tactical entry and door breaching. The setup is rougly similar to the CQB model of the military Modular Combat System, although the method for fixing the retractable M4 type stock is different.

The M870 Modular Combat System, or MCS, is a modular system based around the M870 shotgun. The MCS comes in a box that contains all the neccessary parts to create three different M870 setups. The full size model with 18 inch barrel is most similar to the tactical models of the M870 with its fixed polymer stock, pistol grip, accessory rails and conventional looks. The CQB version features a stock and pistol grip derived from the M4 carbine and has a shorter 14 inch barrel with flash hider. The smallest setup is the Breacher model with its 10 inch barrel and no stock. The Breacher model may also be fitted under the M4 carbine to form a Masterkey setup.

Scattergun produces several customized M870 models. The most compact model is the Entry model which has a 5 round capacity and a slider with integraded light. The Border Patrol model is a full size model with magazine extension. The Border Patrol Short model is similar but slightly shorter. The FBI model has no magazine extension but features a slider with integrated tactical light. All Scattergun models feature a variety of upgrades including ghost ring sights. Currently many Scattergun modifications are available from Remington as well.

Robar produces several high customized shotguns based on the M870. The Robar Elite is the best known example. The Elite features new sights, a modified barrel, improved trigger, a magazine extension, a new finish and various other improvements. The result is a high quality shotgun at a very high price level.