DMR (designated marksman's rifle)
DMR is an acronym for designated marksman's rifle. A DMR bridges the gap between an infantryman's assault rifle and a dedicated sniper rifle, as DMRs are less maneuverable and usually have smaller magazines than assault rifles, but are still more flexible than a full-size sniper's rifle. Designated marksmen are included in squads or platoons to provide fast, accurate fire at longer ranges than regular infantrymen are capable of, while not being so specialized as to require a spotter for ranging and protection (as a sniper would).
DMRs are usually semi-automatic and chambered in a full-power battle rifle round like 7.62x51mm NATO (.308 Winchester), whereas sniper rifles are often bolt-action and may be chambered in specialized long-range rounds like .338 Lapua Magnum.
DMRs are usually semi-automatic and chambered in a full-power battle rifle round like 7.62x51mm NATO (.308 Winchester), whereas sniper rifles are often bolt-action and may be chambered in specialized long-range rounds like .338 Lapua Magnum.
AR-pattern rifle in a setup typical of a DMR.
DOPE (data on previous engagements), DOPE sheet, DOPE book
A DOPE sheet or DOPE book is a tool used by highly precise shooters. Following a successful hit, the shooter will record data on the shot to assist them in taking a similar shot later. Recorded data usually includes the range of the shot and the elevation and windage adjustments of the scope, but can also include the atmospheric conditions (temperature, humidity, and wind speed/direction), the elevation difference between shooter and target, the speed of the target (if moving), and any other factors that may assist the shooter later. DOPE is specific to a particular barrel length and caliber, and sometimes even to a particular weapon (in highly precise applications), so it is not uncommon for avid shooters to have several DOPE books.
DOPE sheets are a distilled version of the DOPE book, showing the required adjustments for a variety of ranges (under particular atmospheric conditions), and are usually taped to the stock of the rifle itself.
DOPE sheets are a distilled version of the DOPE book, showing the required adjustments for a variety of ranges (under particular atmospheric conditions), and are usually taped to the stock of the rifle itself.
dot sight (electronic sight, reflex sight, holographic sight, reflector sight, collimator sight)
Dot sights have many different names, but they all describe the same thing: non-magnifying or low-magnification weapon sights that superimpose a reticle on the sight lens. Different types of dot sights sights generate the reticle in different ways, though they all provide similar experiences for the shooter. Most dot sights use a LED bulb, luminous tritium, or fiber optics to generate the reticle, while holographic sights use a laser, and a few manufacturers physically etch a reticle onto the lens to provide a black backup reticle when all power sources have been depleted.
Although the underlying technology and proper names of these sights is a mystery to most shooters, one fact that few people will argue is that dot sights are demonstrably faster and more accurate than standard iron sights. Studies comparing electronic and iron sights consistently demonstrate 25-50% improvements in target acquisition speed and shot grouping, even among trained soldiers.
Although the underlying technology and proper names of these sights is a mystery to most shooters, one fact that few people will argue is that dot sights are demonstrably faster and more accurate than standard iron sights. Studies comparing electronic and iron sights consistently demonstrate 25-50% improvements in target acquisition speed and shot grouping, even among trained soldiers.
double-feed
A double-feed occurs when a fired case does not extract from the chamber (FTE), but the action nonetheless attempts to chamber a new round. Double-feeds have a very frightening appearance but are usually not dangerous, as the chambered round has already been fired and is thus harmless. However, should a double feed occur when both rounds are live (unfired), extreme care should be exercised when clearing the action.
Double-feeds can usually be resolved by manually clearing and cycling the action. However, a firearm that consistently double-feeds should be examined by a professional.
Double-feeds can usually be resolved by manually clearing and cycling the action. However, a firearm that consistently double-feeds should be examined by a professional.
Dragunov
See SVD.
drill and tap (D/T, D-T)
A "drill and tap" job on a firearm means that holes have been drilled into the firearm and then threaded to allow a scope mount (or some other accessory) to be bolted on. The name comes from the tools used during the procedure: a drill to make the holes and a tap to cut the threads. Modern firearms are usually drilled and tapped from the factory, but if you want to add a scope or sight to a firearm not originally intended to mount an optic, you will usually need to drill and tap. Some firearms have specially-designed mounts that do not require drilling and tapping, however, the usefulness of these "gunsmith free" mounts varies widely, with some just as effective as drill and tap mounts, and some just about useless.
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