Practice with national-level exam (FACT, FACT Plus, NET, CUET, etc.) mocks, learn from structured notes, and get your doubts solved in one place.
The long-gun taxonomy: bolt-action (Mauser 98, Remington 700, Lee-Enfield SMLE), lever-action (Winchester 1894), pump (Remington 870), semi-auto (AR-15 platform, INSAS 5.56, Springfield M1A), and shotgun action types (break, pump, semi-auto, lever); the difference between rifled slug, buckshot and birdshot loadings; and combination guns (drilling, Cape gun) in hunting casework.
Last updated:
Long guns, defined by barrel length, shoulder stock, and the requirement for two-handed operation, divide forensic casework into two fundamentally different evidence landscapes. A rifle fires a single projectile through a rifled barrel, and the rifling marks on that projectile are the examiner's direct link to the specific weapon. A shotgun fires multiple projectiles (or a single rifled slug) through a smoothbore or minimally rifled barrel, and the lack of conventional striation evidence shifts the examiner's focus to the shot charge, the wad, the over-powder cup, and the crimped hull mouth, all of which carry class and sometimes individual characteristics. Combination guns do both, presenting a third evidence model that mixes rifled and smoothbore forensic signatures in a single weapon platform.
The action type of a long gun, whether bolt, lever, pump, or semi-automatic, determines which marks the fired case carries. A bolt-action leaves deep, well-defined bolt-face marks from the manually operated locking lug; a pump-action leaves pump-stroke extraction marks alongside the standard firing-pin and ejector traces; a semi-automatic lever-delay or gas-operated design leaves gas-port erosion marks on the case body that a manual-action rifle does not. Each of these action signatures narrows the comparison scope before the comparison microscope is even loaded.
Long guns appear in forensic casework across a wider spectrum of contexts than handguns in many jurisdictions. Rural homicides and suicides in India, Australia, Canada, and much of rural Europe and the United States overwhelmingly involve licensed long guns, primarily bolt-action centre-fire rifles and pump or break-action shotguns. Crime-scene reconstruction involving a long gun requires integrating wound ballistics, range-of-firing estimation, bullet trajectory reconstruction, and action-type identification into a single coherent report. This topic provides the taxonomic and mechanical foundation for that work.
Almost every bolt-action service and sporting rifle in the world traces its locking system to Peter Paul Mauser's 1898 design, and the forensic marks that design leaves on fired cases have been read at crime scenes for over a century.
A bolt-action rifle feeds, locks, fires, extracts, and ejects through the manual cycling of a bolt handle. The shooter lifts the handle to unlock the dual forward locking lugs (in a Mauser-type action) from their recesses in the receiver, pulls the bolt rearward to extract and eject the fired case, pushes the bolt forward to strip a fresh round from the internal magazine and chamber it, then rotates the handle down to re-lock. This manual cycle has no automatic component; each shot requires a deliberate firing sequence, which makes the bolt-action slower than a semi-automatic but mechanically more reliable and more adaptable to high-pressure, heavy calibres.
Test yourself on Forensic Ballistics with free, timed mocks.
Practice Forensic Ballistics questionsThe Mauser 98 (Gewehr 98, adopted by the German Imperial Army in 1898) established the controlled-round-feed, dual-locking-lug, non-rotating extractor design that became the template for sporting rifles worldwide. Peter Paul Mauser's receiver design was licensed and adapted into the Springfield M1903 (US Army), the Pattern 14 Enfield and its American M1917 derivative (US and UK World War I service), the Winchester Model 70, and the Remington 700 (introduced 1962, the most commercially successful bolt-action sporting rifle in North America). The Remington 700's firing-pin and breech-face geometry is widely documented in FBI and ATF reference collections because it appears in virtually every rural American county in the United States as both a sporting and hunting arm and as a law-enforcement precision rifle (the USMC M40 series are accurised Remington 700 actions).
The Lee-Enfield Short Magazine Lee-Enfield (SMLE), chambered in .303 British, used a different locking system: the rear locking lugs (rather than the Mauser front locking) give the SMLE a shorter lock time and a reputation for a smoother, faster bolt throw, but the rear-lug design means the bolt face is unsupported by the full stiffness of the Mauser bridge. The SMLE was the standard British and Commonwealth infantry rifle from 1903 through World War II. It continued as the standard Indian Army rifle through 1947 and beyond; modified as the 2A and 2A1 variants (chambered for 7.62x51mm NATO from the 1960s), Lee-Enfield actions remained in Indian service into the 1990s and still appear in licensed civilian inventory. .303 British cases fired in Lee-Enfield actions are identifiable by the extractor ring at the case rim, the shallow rear-locking bolt-face impression, and the specific Lee extractor-jaw mark pattern.
The Mauser 98's controlled-round-feed extractor is a distinguishing forensic mark. Unlike the Remington 700's push-feed design, the Mauser extractor snaps over the case rim as the cartridge is stripped from the magazine, contacting the case rim before the round is fully chambered. This produces a specific extractor mark on the case rim before firing, not during extraction, a subtle but forensically distinguishable feature.
The lever-action and pump-action are historically significant platforms still present in civilian casework, and both generate distinctive extraction marks tied to their manually cycled mechanisms.
The lever-action rifle operates by a downward-and-forward stroke of a lever that forms the trigger guard. The stroke unlocks and retracts the breech bolt, extracts and ejects the fired case, and cocks the hammer; the return stroke strips a fresh round from the tubular magazine and chambers it, then locks the bolt. The Winchester Model 1894 (.30-30 WCF, later .44 Magnum and .357 Magnum chamberings) is the highest-production lever-action rifle in history, with over 7 million manufactured, and it appears routinely in rural North American hunting casework and, less commonly, in Australian licensed-civilian inventory. The Marlin 336 and Henry rifles are current-production alternatives.
The lever-action's forensic mark on fired cases is primarily the extractor type: the Winchester 1894 uses a T-slot extractor that grips the case rim along its full width, leaving a uniform extractor mark with a characteristic width. The ejector in the Winchester 1894 is a spring-steel blade inside the receiver that contacts the case rim on the left side and flicks the case out of the ejection port. The combination of T-slot extractor mark and blade-ejector impact produces a specific mark signature the examiner can distinguish from a bolt-action's extractor claw.
The pump-action rifle (slide-action) uses a fore-end that slides forward and back under manual force. The Remington Model 7600 (formerly the 760 Gamemaster) and the Browning BLR Slide Action are pump-action rifles chambered in centre-fire sporting calibres (.30-06 Springfield, .308 Winchester). The pump-action's extraction stroke is driven by the shooter's rearward pull on the fore-end, which produces a consistent but powerful extraction force. Extraction marks on pump-action rifle cases are typically heavier and more consistent in width than bolt-action cases because the pump stroke is a straight-line, machine-guided motion without the rotational component of a bolt cycle.
In Australian licensed-firearms casework, the National Firearms Agreement of 1996 (post-Port Arthur) prohibited semi-automatic and pump-action rifles for most categories of licensed civilians, limiting legal access to bolt-action and lever-action repeaters. This regulatory change was mirrored by significant shifts in the types of rifles appearing in rural suicide and homicide cases in New South Wales and Victoria from 1997 onward, a pattern documented by the Australian Bureau of Statistics and published in the Australian and New Zealand Journal of Public Health. The forensic implication is that an Australian rural scene involving a pump-action rifle post-1996 is more likely to involve an unlicensed or illegally acquired weapon.
A gas-operated semi-automatic rifle leaves a tell-tale mark on fired cases that manual-action rifles cannot: propellant gas under pressure contacts the case body at the gas port, and this mark is class-characteristic for the gas system design.
A semi-automatic rifle fires once per trigger pull and automatically cycles the bolt to chamber the next round. Two operating principles dominate: gas operation (a gas port in the barrel bleeds propellant gas to drive a piston or the bolt carrier directly) and recoil operation (energy from the bolt cycling under recoil feeds the cycle). Gas operation is overwhelmingly dominant in military and police rifles.
The AR-15 / M16 family (ArmaLite / Colt, 5.56x45mm NATO / .223 Remington) uses a direct-impingement gas system in which a gas tube runs from the barrel port directly into the bolt-carrier key, venting gas directly into the bolt-carrier without a piston. This direct-impingement system leaves a distinctive carbon deposit pattern on the bolt-carrier face and inside the receiver extension, not a diagnostic case mark per se, but a recognised maintenance and examination indicator. The fired case in an AR-15 shows a round firing-pin impression, well-defined breech-face marks from the M16-pattern bolt face, extractor marks at the 3 o'clock position (the AR-15 uses a single extractor), and ejector marks from the spring-loaded plunger ejector inside the bolt face. The plunger ejector is class-distinctive for the AR-15 bolt group and distinguishes AR-15 cases from cases fired in piston-operated 5.56 rifles such as the HK G36 or the FN SCAR-L.
The Indian Small Arms System (INSAS) rifle (5.56x45mm INSAS, a specifically developed cartridge) is the standard Indian Army individual weapon. The INSAS uses a rotating-bolt, short-stroke gas piston system influenced by the AK-47's gas system but with an in-line layout similar to the FN FNC. The INSAS entered service in 1998 and is produced at the Ordnance Factory Tiruchirappalli (OFT) in Tamil Nadu, which also produces the SAF Carbine 9mm and the Trichy Assault Rifle (TAR). The INSAS fired-case signature: the rotating-bolt locking marks on the case body from the three-lug bolt are specific to INSAS geometry. Examiners working Indian army or paramilitary scenes must be aware that INSAS ammunition (headstamped "OFT" + year) differs dimensionally from NATO 5.56x45mm, and that INSAS weapons will chamber NATO 5.56, but NATO weapons should not fire INSAS without dimensional verification.
The Springfield M1A and its military predecessor, the M14 (7.62x51mm NATO), use a gas-operated rotating-bolt system with a piston riding in a tube above the barrel. The M14 was the standard US Army rifle from 1957 to the early 1960s and reappeared as the Mk.14 EBR and M21 sniper system in US military service in Afghanistan and Iraq. The M1A is the civilian-legal semi-automatic version, widely used in precision shooting and appearing in US casework. The M14's bolt-face mark is large (7.62x51mm base is 12mm diameter vs 9mm for 5.56mm), with distinctive extractor marks from the M14's push-feed extractor and a specific ejector-rod impact mark on the case head.
In Germany, the Heckler and Koch G3 (7.62x51mm), designed using Mauser and CETME technology, uses a roller-delayed blowback system unique in the semi-automatic rifle world. The rollers that delay the bolt opening under chamber pressure leave distinctive curved impressed marks on the forward shoulder of the cartridge case, a forensic signature specific to roller-delayed designs (HK G3, CETME, HK33, HK91). German BKA examiners developed the identification protocol for these marks in the 1960s when the G3 entered Bundeswehr service.
A shotgun scene generates a different evidence set from a rifle scene: the fired hull, the wad, and the shot charge are the primary evidence items, and each carries class characteristics that identify the load, the choke, and sometimes the action type.
A shotgun is designed to fire a charge of multiple spherical pellets (shot) through a barrel that is typically smoothbore or mildly choked at the muzzle. The pellets spread laterally after leaving the barrel, and the pattern of pellet strikes on a surface encodes the range, the choke constriction, and the shot load. A single rifled slug may also be fired from a shotgun barrel, producing a wound more like a large-calibre rifle than a multi-pellet spread.
Four action types dominate shotgun design. The break-action (side-by-side or over-under double barrel) is the simplest: a hinge at the receiver allows the barrels to pivot forward, exposing both chambers for loading and ejecting. Break-actions carry either two rounds (the double barrel) or one (single-shot). They leave no extraction mark other than the extractor lip dragging along the case head; ejection is either automatic (auto-ejectors that fire when the top lever is operated) or manual (manual extractors that merely raise the cases for finger removal). The Beretta 686, the Browning Citori, and the Miroku shotguns are over-under break-actions widely used in sport shooting in Europe, Australia, and the United States. In India, licensed civilian break-action shotguns in 12-bore are the most common licensed long gun outside the military and police, and they appear in rural homicide and accidental-discharge cases across all states.
Pump-action shotguns use a sliding fore-end to cycle the action. The Remington 870 (introduced 1950, over 11 million produced) and the Mossberg 500 / 590 are the dominant pump-action designs globally. The Remington 870 is used by the FBI, US Border Patrol, many state police agencies, and numerous international police forces including the New Zealand Police. The UK Home Office issued Mossberg 590A1 shotguns to certain Counter Terrorism Specialist Firearms Officer (CTSFO) units. In India, pump-action shotguns are classified as Prohibited Bore under the Arms Act 1959 because they can fire more than two rounds without reloading, placing them in the same legal category as automatic weapons for civilian licensing purposes (see Section 5 below). Their presence in Indian casework therefore almost always indicates a police, military, or illegally acquired weapon.
Semi-automatic shotguns use either a gas-operated or inertia-operated system to cycle the action. The Browning Auto-5 (1902), designed by John Browning and produced for over a century, was the first successful semi-automatic shotgun. Modern designs include the Benelli M2 (inertia-operated), the Beretta A400, and the Mossberg 940. Gas-operated semi-automatic shotguns leave distinctive bolt-face and extractor marks on the fired case. Inertia-operated designs leave a slightly different extractor mark because the entire bolt group travels rearward on inertia before the extractor claw begins extraction.
| Shot type | Components | Pattern | Range effective | Forensic markers | Typical use |
|---|---|---|---|---|---|
| Birdshot | 100-400+ spherical pellets, 1.5-3mm diameter (shot sizes #12 to BB) | Wide spread, 60-90cm at 25m for IC choke | Up to 40m for hunting birds; incapacitation limited beyond 20m | Wad, over-shot card, shot pattern, pellet size and hardness | Bird hunting; clay target; rural India criminal use in 12-bore licensed shotguns |
| Buckshot | 9-36 spherical pellets, 6-9mm diameter (00 Buck = 8.38mm) | Medium spread, 20-35cm at 15m | Effective to 30-40m; lethal out to 50m | Wad design (often one-piece), pellet diameter, pellet-pattern area on target |
The forensic examination of a shotgun hull focuses on: the primer impression (typically a larger primer than a rifle cartridge, with a round central impression in a large primer pocket), the crimp deformation at the case mouth (star crimp or roll crimp, each indicating the original factory load configuration), and the wad recovered from the scene or the wound. The wad is a critical piece of evidence for range-of-firing estimation because wad travel distance from the muzzle is calibrated for specific loads. The Modified Griess test and macro-photography of the wad marks on a target surface are standard tools for range-of-firing analysis in shotgun cases.
Combination guns appear almost exclusively in hunting casework, but they present the examiner with a dual-evidence set: one barrel generates rifle-case evidence, the other generates shotgun-hull evidence, and the specific barrel arrangement must be established before any comparison work.
A combination gun is a firearm that incorporates two or more barrels in different calibre or bore classes in a single weapon. They range from simple two-barrel designs to the elaborate German Drilling (three barrels). The forensic examiner's challenge with a combination gun is to identify which barrel fired which piece of evidence.
The Cape gun (side-by-side double with one rifled barrel in a centre-fire rifle calibre and one smoothbore barrel in a shotgun gauge) was designed for African and Indian colonial hunting in the late nineteenth and early twentieth centuries, allowing a single weapon to address both dangerous game (the rifle barrel) and bird and game at closer range (the shotgun barrel). The Cape gun appears in South African, Kenyan, and Indian colonial hunting casework from the late 1800s onward, and surviving examples with usable barrels still appear in Indian licensed-civilian inventory. The rifled barrel leaves conventional striation marks on bullets; the shotgun barrel leaves a hull and wad pattern. The two barrels share a common receiver but have independent firing mechanisms, and the fired case from each barrel is distinct in calibre and primer-pocket geometry.
The German Drilling (from "drei" for three) typically has two side-by-side shotgun barrels above a single rifle barrel. The dominant historical configuration was 16-bore by 16-bore over 9.3x74R or 7x65R centre-fire rifle. The drilling appears in European and South American hunting casework and was issued to German Luftwaffe aircrew in the Afrika Korps as a survival weapon (the Luftwaffe M30 Drilling, chambered 12-bore x 12-bore over 9.3x74R). The drilling's forensic mark set includes two separate shotgun hull impression types from the side-by-side barrels and one rifle case impression from the under barrel, all sharing the same external hammer or internal mechanism timing.
The over-under rifle-shotgun (such as the Savage Model 24, a long-running American combination gun in configurations such as .22 LR over .410 bore, or .22 LR over 20-gauge) is a simpler design common in US rural casework. The Model 24 was produced from 1950 to 1988 and appears in US rural homicide and suicide casework because of its low purchase price and widespread availability. Distinguishing which barrel of a Savage 24 fired the evidence round requires the examiner to compare the bore diameter (rifled vs smoothbore), the bore dimension (relevant to slug or pellet sizing), and the case impression, because the two barrels have independent extraction and ejection mechanisms.
In India, the combination gun is not specifically addressed by the Arms Act 1959, but the general rule is that the most restricted barrel's classification applies to the entire weapon. A Cape gun with a rifle barrel in a Prohibited Bore calibre would be classified as a PB weapon, making the entire combination gun subject to PB restrictions, not just the shotgun barrel.
India's long-gun casework is shaped by the Arms Act 1959's two-tier classification, which places most repeating rifles and semi-automatic long guns in the Prohibited Bore category accessible only to military and police, concentrating licensed-civilian long-gun evidence in single-shot and double-barrel shotguns and bolt-action rifles.
The Arms Act 1959 restricts the Indian licensed-civilian long-gun market in ways that directly shape the forensic evidence landscape. The NPB (Non-Prohibited Bore) category, open to licensed civilians with a standard licence, includes single-shot shotguns, double-barrel shotguns, and bolt-action rifles in non-military calibres (primarily .315 bore and .22 LR, as well as 12-bore, 16-bore, and 20-bore shotguns). The PB (Prohibited Bore) category, restricted to military, paramilitary, and authorised police personnel, includes all arms capable of firing military calibres (including 7.62x51mm, 5.56x45mm INSAS, 7.62x39mm, and all pistol calibres above .380 ACP for rifles) and all weapons capable of automatic or semi-automatic fire.
In practice, this means that the vast majority of licensed-civilian long guns encountered in Indian casework are: the IOF .315 bore double-barrel shotgun (produced at the Gun and Shell Factory Cossipore), the IOF 12-bore double-barrel (available both in break-action and, until its classification was updated, in single-barrel form), and the IOF .22 LR bolt-action sporting rifle. These three weapons dominate Indian licensed-civilian long-gun homicide and accidental-discharge casework.
The INSAS rifle in Indian military and paramilitary (CRPF, BSF) casework is a distinct evidence type. The INSAS was designed at the Armament Research and Development Establishment (ARDE), Pune, with input from Small Arms Factory Kanpur and is produced at Ordnance Factory Tiruchirappalli. The INSAS uses a 20-round or 30-round STANAG-compatible magazine and fires the 5.56x45mm INSAS cartridge. From 2019, India has been phasing in the SIG 716i rifle (7.62x51mm NATO, gas-operated semi-automatic) for units facing direct combat roles, beginning with the Army's special forces and frontline troops; the SIG 716i is a US-manufactured weapon, produced at SIG Sauer's facility in New Hampshire, and its reference marks and comparison data are available in the US ATF/FBI reference collections.
The Lee-Enfield SMLE .303, while largely replaced in military service, remains in Indian licensed-civilian inventory (licensed as a sporting rifle in .303 British) and occasionally surfaces in rural homicide and custody cases. The .303 British case is a rimmed, bottle-necked cartridge with a 13.9mm rim diameter, distinctive in comparison with the rimless cases of NATO calibres, and easily identified at a scene.
Under the Arms Rules 2016 (promulgated under the Arms Act 1959), every licensed firearm in India must be registered with the District Arms Magistrate, with the registration number engraved on the frame. The registration number is the primary trace link between a recovered long gun and its licensed owner. Recovery of a long gun without a registration number, or with an obliterated number, is prima facie evidence of an unlicensed weapon and triggers the serial-number restoration examination as the next step.
A fired 7.62x51mm NATO case recovered from a crime scene shows deep, dual locking-lug impressions on the case body at 12 o'clock and 6 o'clock, a round firing-pin impression, and a non-rotating extractor mark where the extractor claw engaged the rim before the round was fully chambered. Which action type is most consistent with these marks?
| US/EU police duty load; Remington 870 or Mossberg 500 in law enforcement |
| Rifled slug | Single cylindrical or Foster-type slug, 28g to 42g | No spread; single-projectile wound channel | Accurate to 75m (smooth bore); 150m with rifled barrel | Rifling marks on slug from barrel choke or rifled slug barrel; bore diameter; slug base deformation | Deer hunting; German Polizei slug load; US rural police load; high wound severity |
| Brenneke slug | Attached wad slug; stabilising wad attached to base | Single-projectile; wad stays with slug until target | 75-100m | Wad-slug assembly; muzzle-velocity inference from deformation | German, Austrian, Scandinavian hunting casework; police use in EU |