Shotgun Choke Conical Geometry for Steel Shot Stress
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Solution Overview
Problem
Existing chokes for smoothbore rifle barrels are not suitable for steel ball ammunition due to the significant force exerted by steel balls, causing swelling and weakening of the choke and barrel, and fail to maintain high exit speed and achieve tight sheaves.
Innovation Solution
Modifying the internal surface of the choke by machining it to a conical shape over the entire length, eliminating the interface between the conical and cylindrical portions, which reduces stress and maintains diameter difference, allowing for gradual reduction in diameter and improved stability and exit speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a choke with conical and cylindrical portions is used, then the shot pattern can be concentrated and stabilized, but steel shot exerts significant stress causing the choke to swell and weaken
Solution Approach 1:
The invention changes the geometric parameters of the choke by eliminating the cylindrical portion and extending the conical portion over the entire length. This parameter change modifies how steel shot interacts with the choke, distributing stress more evenly and preventing the swelling that occurs at the interface between conical and cylindrical sections.
2Manufacturing precision
If the choke outlet diameter is reduced for tight shot pattern, then shot concentration improves, but steel shot velocity decreases and pattern increases
Solution Approach 1:
The invention uses a curved generatrix for the conical portion, creating a smooth, continuous curvature rather than straight lines. This curved geometry allows for gradual diameter reduction that maintains shot pattern tightness while minimizing abrupt transitions that would decelerate steel shot.
3Strength
If steel shot ammunition is used, then ammunition hardness increases, but the force exerted on the choke causes swelling and weakening
Solution Approach 1:
The invention segments the choke into only a conical portion without a distinct cylindrical section, eliminating the interface where stress concentrates. This segmentation strategy redistributes the force from hard steel shot more uniformly throughout the choke structure, preventing localized swelling and weakening.
4Ease of operation
If a second conical section increasing diameter is added, then steel shot can pass through, but velocity is lost and shot pattern increases
Solution Approach 1:
The invention extracts the second conical section that increases diameter, keeping only the conical portion that narrows the diameter throughout its entire length. This extraction eliminates the velocity-loss mechanism associated with diameter expansion while still allowing steel shot to pass through the narrowed choke effectively.
Data Source
Figure 1~4
Figure 5~7
Figure 8~9
AI summary
The invention relates to a method for modifying a choke (5) for a smoothbore shotgun barrel (1) comprising the following steps: - providing a choke (5) having a through orifice (6) delimited by an internal surface (7), the internal surface (7) comprising a conical portion (8) and a cylindrical portion (9) with a circular cross-section, the conical portion (8) and the cylindrical portion (9) extending over a dimension equal to a predetermined length L, - introducing a conical reamer (12) into the through orifice (6) on the side of the conical portion (8), - machining with the conical reamer (12) the internal surface (7) of the choke (5) so that after machining the internal surface (7) has a conical shape extending in the first direction over the entire predetermined length L. The invention also relates to chokes (5) for smoothbore shotgun barrels (1).