Weapons used in MilSim are commonly replica toy guns. Airsoft guns are used more often in MilSim than paintball guns due to their availability as a realistic replica weapons without any modification.
In the past, due to the unrealistic nature of the performance of airsoft and paintball weapons, they were seldom used in real-world training environments. Instead, specialized non-lethal ammunition or blanks are used in conjunction with infrared targeting systems. More recently however, advances in airsoft replica authenticity and function have led numerous law enforcement and military units using them to train in CQB/CQC environments. Airsoft and paintball guns though previously not considered realistic by the US Department of Defense or major police departments for training purposes are becoming more so due to increases in realism and function, especially airsoft.
MilSim most often falls into two different categories: reenactment and simulation. Reenactments focus on a particular event in history and aim to provide the most accurate representation of the time period, events, and outcomes of the historical event. Simulation, however, may only focus on a particular time period and representation of which course a particular situation may have taken in history.
Airsoft is a sport in which individuals attempt to participate in the simulation of military combat also called MilSim or law enforcement-style combat.
Some airsoft teams specialize in MilSim and historical reenactment intended to get the participant "inside the head" of the characters from history. This gives participants a chance to pretend they are part of recent history. Occasionally airsoft groups have ex-military members seeking the camaraderie of their old units without the commitment. Airsoft guns are typically battery or gas-operated, holds dozens to hundreds of plastic BBs (depending on magazine-type), and are much quieter than a real firearm. They are typically only accurate for a hundred feet. Some newer gas-operated models feature realistic blowback action and bolt cycling and some even have shell ejection and recharge that emulate their real-world counterparts exactly. Players are commonly unable to engage opponents at realistic distances in outdoor fields. There are various weapons classes that are used in the sport, I.E. Assault Rifles, Support Weapons (Machine Guns), Sniper Rifles, etc., that dictate the role of the individual player. Indoors however, airsoft guns have virtually identical accuracy to their real steel counterparts. Players often lack real-world tactical training, and many in-game combat deaths and injuries come from simulated artillery and other explosives as well as small arms fire.
Airsoft has its roots in late-1980s East Asia, specifically Japan where firearms were difficult or impossible to obtain due to local laws, so people sought a legal alternative for enjoying their passion. Airsoft is still today most popular in several Asian regions, such as Japan, Mainland China, Taiwan, Hong Kong, Macau, South Korea, and to a certain extent, the Philippines, and Indonesia. The vast majority of airsoft guns, accessories and after market upgrade parts are also manufactured in these countries.
There is also a growing interest in North America with several promoters throughout he nation the largest two being MilSim West and American MilSim , Canada, United Kingdom, Germany, Austria, Switzerland, France, Spain, Russia, Sweden, Poland, Lithuania, Portugal, Greece, Finland, Norway, Italy, Belgium, the Netherlands, Denmark, Ireland, Chile, Argentina, Puerto Rico, the Dominican Republic, and South Africa, bolstered by an active and expanding Internet scene.
The United Kingdom's MilSim scene includes a number of airsoft event organizers who specialize in MilSim events run in conjunction with Live Action Role-Players (see LARP) at British Army training facilities such as Copehill Down and Catterick Garrison.