Staff Writer (Updated: 8/20/2016):
The Model 870 is a wholly-conventional pump-action slide shotgun offering. The design constitutes a rectangular receiver housing the requisite internal action, a forend slide assembly over the tubular magazine with barrel mounted over and a full shoulder stock incorporating a pistol-type grip. Shells are loaded individually through the underside loading gate to which the operator then manages the pump-action slide to introduce a fresh shell into the chamber whilst ejecting any possible spent casing within. Spent casings are ejected through an oblong port along the right side of the receiver. Depending on the model and caliber, the M870 can house four to seven shells in its tubular magazine with an extra shell already in the chamber ready-to-fire. Barrel lengths also vary based on model and chosen barrel installation and this directly effects overall weight of the system (7lbs to 9lbs). Iron sights are provided though rifle-type scopes can be affixed as required through special added mounts.
The M870 has appeared in numerous forms throughout its long and storied history. The firearm has come available in the well-accepted 12-gauge form but has also appeared in 16-, 20- and 28-gauge as well as a .410 bore system capable of firing slug, buckshot and flare rounds. One of the more popular M870 sub-models is the "Wingmaster". Accessories include a forward hand grip along the slide with tactical pistol grip for a more compact overall form.
Operators of the M870 are many and include Australia (military), Austria (special forces), Bangladesh (army), Canada (army, police); China (army, marines), Finland (army), Germany (army), Greece (special forces, police), Hong Kong (police), Hungary (military), Ireland (army), Israel (army), Luxembourg (special police), Malaysia (special forces), South Korea (navy special forces), Sweden (army), Switzerland (army), the United Kingdom (special forces) and the United States (military, border patrol, security and police). The M870 is under illegal production in China under the NORINCO brand label as the HP9-1.