Designated marksman rifle

A designated marksman rifle (DMR) is a modern scoped high-precision rifle used by infantrymen in the designated marksman (DM) role. It generally fills the engagement range gap between a standard service rifle and a dedicated sniper rifle, at around .
DMRs, unlike the often bolt-action sniper rifles, are almost always semi-automatic as these have higher rates of fire and typically larger magazine capacities (10, 20, or 30 rounds depending on the firearm and operational requirements) to allow rapid engagement of multiple targets. These rifles have to be effective, in terms of hit rates and terminal ballistics, at application ranges exceeding those of ordinary assault rifles and battle rifles, but do not require the extended-range performance of a dedicated sniper rifle. DMRs needs to function as part of squad (and possibly at close quarters) and often share some basic characteristics with sniper rifles when compared to other weapons carried in the DM's platoon. They typically have telescopic sights for more detailed observation and aiming, often also quick-deployed bipod for optimized accuracy, reduced recoil and better stability, and an adjustable stock for better ergonomics.
Comparison to sniper rifles, battle rifles, and assault rifles.
Most designated marksman rifles are based on modified designs of an assault rifle currently issued by a nation's military, or on a battle rifle that was formerly issued. The ammunitions used are often of the same caliber as that of the squad automatic weapons within the same combat unit, typically a fully powered cartridge such as the 7.62 mm NATO. For example, battle rifles such as the M14, FN FAL, AR-10 and Heckler & Koch G3 were largely replaced during the 1980s and 1990s by modern assault rifles firing the 5.56 mm NATO intermediate cartridge, but many were accurized and retained as DMRs.
Conversely, some nations have also built rifles that were designed for the designated marksman from the ground up. Examples include the Soviet SVD and Chinese QBU-88.
Sights.
Some designated marksman rifles will have some type of optical sight with a higher magnification level than the standard issue rifle. For example, the SDM-R issued to the United States Army is fitted with a Trijicon 4× ACOG, while the standard-issue M4 carbine is equipped with an unmagnified Aimpoint CompM2 or CompM4. Commonly, the sighting system will be the only difference between the standard rifle and the designated marksman rifle, as is the case with the F88S DMR issued to the Australian Army.
Sniper rifles often have even greater magnification than designated marksman rifles outfitted with magnification, for example, the M110 SASS used by the United States Army, is equipped with a Leupold 3.5-10× variable-power scope. However, some designated marksman rifles, such as the Mk 12 Special Purpose Rifle or the USMC Squad Advanced Marksman Rifle are fitted with scopes with similar magnification.
Barrels.
In some cases, the designated marksman rifle will have a longer barrel than the standard issued rifle. For example, until October 2015, when the M4 carbine was approved as the new standard issue rifle, the M16A4 rifle was still standard issue throughout the United States Marine Corps. The barrel on the Mk 12 Special Purpose Rifle, the current rifle used by the squad designated marksman in the USMC, is only 500 mm (18 in) long - 50 mm (2 in) shorter than the barrel on the standard rifle. This is no longer the case, however, as the M4 carbine has a barrel length of only 370 mm (14.5 in). Also, some rifles, such as the F88S Austeyr, have a barrel that is the same length as the standard service rifle. The FD-200 has an accurized barrel, also found on designated marksman rifles.
Most sniper rifles, such as the Accuracy International Arctic Warfare, have a barrel with a length of 610 mm (24 in) or greater. Only the Dragunov sniper rifle (SVD) and similar designated marksman rifles have a barrel of this length. The designated marksman rifles based on the M14 have barrels 460–560 mm (18–22 in) long.
Ammunition.
In most cases, a designated marksman rifle will share the caliber and possibly even the ammunition type used by standard issue rifles. DM rifles may be issued with standard ball ammunition, or special match grade loads, such as 7.62 mm NATO 'M118LR' sniper round. Sniper rifles are (almost exclusively) deployed with match grade ammunition in order to take advantage of their full effective range and accuracy potential.
In the U.S. military, designated marksman rifles chambered for 5.56 mm NATO have available the 5 g (77 grain) match grade Mk 262 Mod 0/1 cartridge that enhances the effective range to roughly .
Action.
All designated marksman rifles in use today are semi-automatic, some with select fire. Sniper rifles are generally bolt action rifles, but can also be semi-automatic.