Necking sizing die for shoulder breeching rifle cartridges

Abstract

A neck sizing die for shoulder breeching ammunition cartridge cases that uses the shoulder to align the case, not the body. Alignment occurs before resizing. Resizing is done in a two-step process: a bushing is used to shrink the neck diameter and then an expansion button is used to increase it. Bushing and button diameters are highly selectable and easily changed. Cone-and-cup interfaces ensure concentricity of the case shoulder to the bushing or button. The unique alignment technique and two-step sizing method produces a case with a neck having an interior diameter of the user's choice with the interior wall of the neck aligned to the shoulder. This results in a case that will more reliably position the bullet concentric with the bore of the barrel than existing tools and methods.

Claims

1. An apparatus for forming or reforming an ammunition cartridge case, said case comprising a head, said case further comprising a body, said case further comprising a conical shoulder, said case further comprising a neck, said apparatus comprising: a case-carrier, said case-carrier comprising a chamber into which said case is inserted during operation of said apparatus, said chamber comprising a conical shoulder with a cone angle and median diameter substantially equal to the cone angle and median diameter of said shoulder of said case; a shell comprising a bore housing said case-carrier, said case-carrier translating within said bore of said shell during operation of said apparatus, said bore terminating in a conical shoulder co-axial with said bore; a die-head comprising a conical shoulder having a cone angle and median diameter substantially equal to the cone angle and median diameter of said shoulder terminating said bore in said shell, said die-head being pressed into said shoulder terminating said bore in said shell during operation of said apparatus; said die-head further comprising a bore into which said neck of said case is pressed during operation of said apparatus; a means by which a compressive force can be maintained across a conical interface between said shoulder of said case and said shoulder of said chamber of said case-carrier, said means simultaneously maintaining a compressive force across a conical interface between said shoulder of said die-head and said shoulder terminating said bore in said shell, said means establishing said compressive forces during operation of said apparatus prior to direct contact between said neck of said case and said die-head, said compressive forces originating in a compressive force applied between said head of said case and said die-head, said means including a spring between said case-carrier and said shell.

2. The apparatus according to claim 1, wherein the die-head is replaceable with a die-head having a cylindrical protrusion that is inserted into said neck of said case during operation of said apparatus.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 illustrates, in cut-away profile view, the preferred embodiment of the Shoulder Breeching Neck Sizing Die with a bushing installed and a case inserted into the die. All parts of the die are made of tool steel or similar material. A cartridge case (1) is inserted into a chamber in the case carrier (2); which terminates with a conical cup (2a) having a nominal diameter and cone angle that matches the shoulder (1a) of the case. A spring (3) sits between the case carrier (2) and the shell (4). The upper end of the shell (4) terminates with a conical cup (4a). A bushing (5) sits in the conical cup (4a) of the shell (4); it has a conical shoulder (5a) with a cone angle and nominal diameter matching the conical cup (4a) of the shell (4), a blind bore (5b) that is co-axial with the shoulder (5a), and a semi-circular push-point (5c) on the top. A cap (6) sits over the bushing (5), resting on the push-point (5c).

(2) FIG. 2 illustrates a button (7) which can replace the bushing (5). The button (7) has a conical shoulder (7a) matching the cup (4a) of the shell (4), a cylindrical tip (7b) coaxial with the shoulder (7a), and a push-point (7c).

DETAILED DESCRIPTION OF THE INVENTION

(3) The Shoulder Breeching Neck Sizing Die reshapes the neck (1b) of a case (1) in a unique way that reforms the interior of the neck into a cylinder of a specified diameter that is concentric with the shoulder (1a). The preferred embodiment presented here is for use with an arbor press, which is favored by many competitive shooters. With minor changes to the exterior a similar die can be used in other types of presses as well.

(4) This die presents a unique approach to controlling concentricity based upon the observation that if two conical surfaces having the same cone angle and median diameter are fully in contact with each other then the axis of those two surfaces must be co-axial. (For the purposes of this invention, if two things are co-axial they are also concentric.) Therefore, all non-moving critical interfaces in this die are conical surfaces with matching cone angles and median diameters. The case (1) interfaces with the case carrier (2) at the shoulder (1a) by means of a conical cup (2a) with a matching median diameter and cone angle. This is the only contact point between the case (1) and case carrier (2). The bushing (5) and button (7) have conical shoulders (5a and 7a) with median diameters and cone angles that match the conical cup (4a) in the shell (4). This ensures that the bushing bore (5b) and button tip (7b) are co-axial with the case shoulder (1a).

(5) This die design takes a unique two-step approach to resizing the neck (1b). In the first step the bushing (5) is used to reduce the neck diameter. In the second step the bushing (5) is replaced with the button (7), which is then used to expand the interior of the neck (1b) while simultaneously aligning it to the case shoulder (1a).

(6) Bushings (5) will be made in a fine gradation of bore (5b) diameters. For the first step in the process the user will select a bushing (5) with a bore (5b) having the proper diameter and place it into the cup (4a) in the shell (4) and then cover it with the cap (6). The proper diameter will be that which results in an interior neck diameter that is slightly smaller than what the final interior diameter needs to be. A case (1) is inserted into the case carrier (2) and the assembly is placed under an arbor press and compressed.

(7) When the assembly is compressed an important sequence of events takes place. First, the ram of the arbor press will press on the cap (6), which presses on the push-point (5c) (a hemispherical bump located in the center of the top of the bushing), which ensures that the force from the press is directed along the axis of the bushing (5). This compresses the bushing shoulder (5a) against the cup (4a) in the shell (4). This ensures that the bushing bore (5b), which is co-axial with the bushing shoulder (5a), is now also co-axial with the cup (4a) in the shell (4). Simultaneously with this the spring (3) transfers this compressive force from the shell (4) to the case carrier (2), which presses the conical cup (2a) against the case shoulder (1a), which presses the case (1) against the base of the arbor press. This compressive force ensures that the case shoulder (1a) is co-axial with the conical cup (2a), which is co-axial with the shell (4), which is co-axial with the bushing bore (5b).

(8) Then, after the above alignment process takes place, the first step in the resizing process is concluded upon further lowering of the arbor press ram, which compresses the spring (3), which causes the case carrier (2) to slide inside the shell (4), which causes the bushing bore (5b) to be pressed onto the case neck (1b), which reduces the neck diameter while also forcing it to become co-axial with the case shoulder (1a).

(9) For the second step in the resizing process the bushing (5) is replaced with a button (7), which will be made in a fine gradation of tip (7b) diameters. The user will choose a button (7) with a tip (7b) diameter that is the same as the desired final neck (1b) interior diameter and place it in the cup (4a) of the shell (4). The cap (6) is replaced and the assembly is once again compressed with an arbor press. The same sequence of events takes place: first, the various parts of the assembly settle into alignment with each other so that the tip (7a) of the button (7) becomes co-axial with the case shoulder (1a); then, the tip (7a) is pressed into the case neck (1b). The final result is a case (1) with a neck (1b) having an interior surface that is known to be cylindrical; has a known diameter; and is co-axial with the case shoulder (1a).