Sub-Sonic Firearm Barrel Shallow Rifling for Trajectory Precision
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Solution Overview
Problem
Achieving flight trajectory precision with subsonic bullets has proven difficult due to mass imbalance and streamlining issues in firearm barrels, leading to inconsistent bullet paths and impact points, as the slow velocity of subsonic bullets allows for more time for disturbances and reduced gyroscopic effects.
Innovation Solution
A firearm barrel design with multiple shallow rifling grooves that form raised lands on the bullet, optimizing the bullet's flight trajectory by reducing buffeting effects and improving sealing, with a twist angle and land geometry that minimizes dynamic imbalance and turbulence, ensuring at least 50% reduction in buffeting and improved sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional barrel designs are used with subsonic bullets, then the bullet can be fired, but the flight trajectory precision deteriorates due to mass imbalance and streamlining issues
Solution Approach 1:
The rifling is segmented into multiple shallow grooves (at least 10 grooves) rather than traditional deep single grooves. This segmentation creates multiple small lands on the bullet surface, which reduces the buffeting effect from any single land-groove interaction and distributes the sealing function across multiple contact points, thereby improving flight trajectory precision.
Solution Approach 2:
The groove depth is locally optimized to be shallow (0.0003 to 0.003 inches) rather than uniformly deep throughout the rifling structure. This local quality change reduces the height of lands on the bullet, minimizing turbulence and buffeting in the critical muzzle exit region while maintaining adequate sealing through the increased number of grooves.
2Speed
If the bullet velocity is reduced to subsonic levels, then the bullet can achieve desired subsonic performance, but the gyroscopic effect is reduced and flight trajectory becomes less precise
Solution Approach 1:
The rifling parameters are changed from traditional deep grooves with fewer segments to shallow grooves with at least 10 segments. This parameter change optimizes the land height and distribution to maintain gyroscopic stability at subsonic velocities by reducing turbulence and buffeting effects that would otherwise disrupt the bullet's flight path.
3Reliability
If traditional rifling groove depths are used, then the bullet can be effectively sealed and propelled, but the lands created cause increased turbulence and buffeting in flight
Solution Approach 1:
The sealing function is segmented across multiple shallow grooves rather than achieved through a single deep groove. This creates multiple shallow lands that collectively provide adequate sealing while minimizing the height of individual lands, thereby reducing turbulence and buffeting in flight.
Solution Approach 2:
Instead of using a single deep groove for sealing, the design uses excessive action by creating at least 10 shallow grooves. This over-sealing approach ensures adequate propellant gas sealing while the shallow depth of each groove prevents excessive land height that would cause turbulence.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The barrel design enhances the precision of subsonic and transonic bullet flight trajectories by reducing buffeting and dynamic imbalances, resulting in more consistent impact points and improved accuracy by ensuring a uniform obturation and aerodynamic surface for the bullet.
Implementation Method 1
The relatively slow rotation of the sub-sonic bullet also reduces the gyroscopic effect of the spinning bullet, making any asymmetric weight distribution within the fired and obturated bullet more apparent
Implementation Method 2
the cartridge case containing a propellant, the propellant producing a propellant pressure upon ignition of the propellant
Implementation Method 3
The buffeting effect upon the bullet in flight by a normal shock wave upon the raised bullet lands is reduced by the plurality of bullet lands and the reduced height of each of the plurality of bullet lands
Data Source
AI summary
A barrel for use in a firearm optimized to fire subsonic ammunition with high precision. The barrel groove diameter being within 0.0003 inch of the nominal bullet diameter and the barrel has at least 8 rifled grooves. Each of the plurality of rifling grooves has a sidewall formed from the bore diameter to the groove diameter, wherein the sidewalls formed are substantially parallel and the depth of each of the rifling grooves is shallow. The bullet is obturated as the bullet is forced down the bore. The plurality of shallow barrel grooves forming a plurality of raised lands upon the bullet. The obturated bullet having at least 50% lands formed around the circumference of the bullet body. The buffeting effect upon the bullet in flight by a transition shock wave upon the raised bullet lands is reduced by the plurality of bullet lands and the reduced height of each of the plurality of bullet lands.