General Rifling Characteristics (GRC)
Definition
The class-level barrel properties (land count, groove count, land width, groove width, twist direction, twist rate) that allow a fired bullet to be compared against a reference database of weapon makes and models.
- Properties measured
- Land/groove count, land/groove width, twist direction, twist rate
- Evidence level
- Class characteristic, not individualising
- Twist direction options
- Right-hand or left-hand
- Typical use
- Narrows a bullet to a list of compatible makes/models
Common questions
Can GRC alone identify the specific gun that fired a bullet?+
No. GRC narrows the pool of possible make and model combinations, but only individual toolmark characteristics such as microscopic striations can link a bullet to one specific barrel.
Why do different manufacturers produce different GRC?+
Rifling is cut or formed using different manufacturing processes and tooling, and each firearm maker selects its own combination of land and groove counts, widths, and twist rate.
Does barrel wear change the recorded GRC over the life of a weapon?+
The class dimensions set by the original rifling stay fixed, though heavy wear can round land edges and reduce impression clarity without altering the underlying count or width figures.
Related terms
- BKA
- Bundeskriminalamt, the German Federal Criminal Police Office, which operates the German GRC and ballistic identification database feeding the European EBIS network.
- CFSL
- Central Forensic Science Laboratory: a central government lab operating under DFSS. India has CFSLs at New Delhi, Hyderabad, Chandigarh, Kolkata, Pune, Guwahati,...
- Grooves
- The recessed channels cut into a rifled barrel between the lands. They create raised land impressions on a fired bullet's surface.
- Lands
- The raised ridges of a rifled barrel. Lands engrave groove impressions into the surface of a passing bullet. They are the harder...
- Left-Hand Twist (LHT)
- Rifling that spirals counterclockwise toward the muzzle. The defining house convention of Colt Manufacturing Company and of the Lee-Enfield rifle family.
- NABIS
- National Ballistics Intelligence Service; the UK police intelligence service that maintains a national headstamp and firearm reference collection and coordinates ballistic intelligence...
- Polygonal Rifling
- A rifling form that uses a rounded hexagonal or octagonal bore profile instead of discrete lands and grooves. Characteristic of Glock barrels;...
- Rate of Twist
- The barrel length required for the rifling to complete one full helical revolution, expressed as a ratio (e.g. 1:9 means one complete...
- Right-Hand Twist (RHT)
- Rifling that spirals clockwise toward the muzzle when viewed from the breech. Used by the majority of the world's firearm manufacturers.