Pressed head
The invention relates to a method of improved ammunition production, more specifically to an improved pressed metal head component suitable for a polymer tube cartridge The invention relates to a method of drawing and forming a metal head unit for use with a polymer case to form a polymer cartridge for use in a rifled barrel, comprising the steps of i) providing a metal cup drawing it through one or more dies to provide a case tube, wherein the case tube has a closed head end with a first outer diameter and an elongate open end, ii) trimming the elongate open end to form a metal coupling protrusion, said metal coupling protrusion with a second outer diameter, wherein the first diameter and second diameter are the same, iii) forming, a primer cavity into the closed head end, iv) forming internal and external features in the closed head end, v) forming by a heading process, an enlarged head rim on the closed head end, such that said enlarged head rim has a third diameter which is larger than the second diameter of the open end.
1. A method of drawing and forming a metal head unit for use with a polymer case to form a polymer cartridge for use in a rifled barrel, the method comprising:
drawing a metal cup through one or more dies to provide a case tube, wherein the case tube has an elongate open end and a closed head end with a first outer diameter;
trimming the elongate open end to form a metal coupling protrusion, said metal coupling protrusion with a second outer diameter, wherein the first outer diameter and the second outer diameter are substantially the same;
forming a primer cavity into the closed head end;
forming internal and external features in the closed head end; and
forming, by a heading process, an enlarged head rim on the closed head end, such that said enlarged head rim has a third outer diameter which is larger than the second outer diameter of the open end.
2. The method according to claim 1 , further comprising:
forming a head stamp on the enlarged head rim, and piercing a through fire hole, and forming an ejector groove under the enlarged head rim.
3. The method according to claim 1 , wherein the polymer case is located inside, outside, both inside and outside, or at least in part over the second outer diameter of the metal coupling protrusion.
4. The method according to claim 3 , wherein an outer diameter of the polymer case and the third outer diameter of the enlarged head rim are substantially the same.
5. The method according to claim 2 , wherein the enlarged head rim is formed by a heading process which simultaneously applies the head stamp.
6. The method according to claim 1 , wherein the third outer diameter of the enlarged head rim is in the range of from 105% to 115% of the second outer diameter.
7. The method according to claim 2 , wherein there is a further circumferential groove below the ejector groove, to accommodate a retaining portion of the polymer case.
8. The method according to claim 1 , wherein said polymer case comprises a polymeric coupling end, and an open end for receiving a projectile or a closed end for forming a blank.
9. The method according to claim 8 , wherein the polymeric coupling end engages with the metal coupling protrusion.
10. The method according to claim 8 , wherein the polymeric coupling end is a female coupling portion with at least two polymeric skirt portions which engage with the metal coupling protrusion.
11. The method according to claim 10 , wherein one of the at least two polymeric skirt portions is an outer polymeric skirt portion, which comprises a retaining portion of the polymer case, which engages with a circumferential groove of the metal head unit.
12. The method according to claim 10 , wherein one of the at least two polymeric skirt portions is an inner polymeric skirt portion, which comprises a further retaining portion, which engages with a flash hole of the metal head unit.
13. The method according to claim 1 , wherein the polymer case is fixed to the metal coupling protrusion.
14. The method according to claim 1 , wherein the polymer case is formed from thermoset, thermoplastic, block polymers, co-polymers, elastomers, fluoroelastomers, fibre reinforced polymer composites, or combinations thereof.