PELIN TOROLF (FI)
| FR1557440A | 1969-02-14 | |||
| US2901814A | 1959-09-01 | |||
| US4359810A | 1982-11-23 | |||
| DE2559239A1 | 1977-07-14 | |||
| US6931776B2 | 2005-08-23 |
| Claims 1. A method of manufacturing the cartridge chamber of a gun consisting of the same piece of metal as the barrel of the gun, characterized in that, in a barrel blank con- sisting of a pipe, an internal pressure pushing the pipe wall outwards is created at the point where the cartridge chamber is to be located, whereby an expansion corresponding to the shape of a cartridge chamber is created in the pipe. 2. A method as defined in claim 1, characterized in that an external mould is fitted at the cartridge chamber against which the metal pipe presses when it is pressed outwards and takes the shape of a cartridge chamber. 3. A method as defined in claim 1 or 2, characterized in that, after the pressing, a reamer is used to finish the inner faces of the cartridge chamber. 4. A method as defined in claim 1, 2 or 3, characterized in that the internal pressure is produced by an explosive forming method. 5. A method as defined in claim 1, 2 or 3, characterized in that the internal pres- sure is produced by a hydraulic pressure method. 6. A method as defined in claim 1, 2 or 3, characterized in that the internal pressure is produced by a metallic mandrel, by pressing inside the pipe. 7. A method as defined in claim 1, 2 or 3, characterized in that the internal pressure is produced by an electric impulse or magnetic forming method. 8. A method as defined in any of the preceding claims, characterized in that the barrel blank consisting of a rifled pipe part and a cartridge chamber part is further equipped with a stiffening outer pipe fitted on the barrel blank and receiving the pressure discharges caused by shooting. 9. A method as defined in claim 8, characterized in that the outer pipe is made of aluminum. 10. A method as defined in claim 8 or 9, characterized in that the barrel blank is cooled down to -70° using carbonic acid, for example, and the outer pipe is heated up to 150 to 200°, before joining them, to make the pipes press together when at the same temperature. |
This invention relates to a method of manufacturing the cartridge chamber of a gun consisting of the same piece of metal as the barrel of the gun.
The barrels of guns, such as hunting rifles, and the cartridge chambers included in the barrels are manufactured using a very old method by
- drilling a hole in a shaft blank to form a pipe
- inserting a mandrel into the hole of the pipe and forging the wall of the pipe against the mandrel to provide the hole with gun barrel rifles
- checking and, if needed, correcting the straightness of the barrel
- drilling a cartridge chamber in one end of the pipe and finishing it with a reamer
- turning a barrel connector thread or bushing on the outer periphery of the car- tridge chamber
- giving a conical outer shape to the barrel by turning and, finally,
- dipping the barrel into an acid mixture to give it a bluish color.
The aim of this invention is to provide a new type of method of manufacturing the cartridge chamber of a gun by shaping one end of the barrel pipe.
The method according to the invention is characterized in that, in a barrel blank consisting of a pipe, an internal pressure pushing the wall of the pipe outwards is created at the point where the cartridge chamber is to be located, whereby an expan- sion corresponding to the shape of a cartridge chamber is created in the pipe.
WO/201 1/012766 discloses a method of manufacturing a gun barrel wherein a thin- walled pipe blank is rolled against a mandrel to rifle the pipe. It is exactly this pipe blank that suits the present invention. Tests have shown that a .222 caliber (5.6 mm) pipe barrel is very well expandable, at the cartridge chamber, to have an inner di- ameter of approximately 9.5 mm. The pipe barrel produced by this method is further equipped with an outer pipe that can be a rigid, stiffening and lightweight aluminum pipe, for example. The dependent claims describe different embodiments of the invention.
The invention will be explained in the following by means of an example.
The method uses a gun barrel blank produced by the manufacturing method dis- closed in WO/2011/012766. In other words, we have a ready-rifled pipe blank, intentionally unrifled at the point where the cartridge chamber is to be located.
An external mould is fitted at the cartridge chamber against which the metal pipe presses when it is pressed outwards and takes the shape of a cartridge chamber.
The pressing is caused by an internal pressure pushing the wall of the pipe outwards to provide the pipe with an expansion corresponding to the shape of a cartridge chamber. The cartridge chamber is plugged and a high hydraulic pressure, of 3000 to 5000 bar, is led into it, resulting in an even force distribution that gives the cartridge chamber a uniform wall structure. After the pressing, a reamer is used to finish the inner faces of the cartridge chamber. The barrel blank consisting of a rifled pipe part and a cartridge chamber part is further equipped with a stiffening outer pipe fitted on the barrel blank and receiving the pressure discharges caused by shooting. The outer pipe can be made of aluminum or some other suitable alloy, or of carbon or glass fiber, for example. The barrel blank is cooled down to -70° using carbonic acid, for example, and the outer pipe is heated up to 150 to 200°, before joining them, to make the pipes press together when at the same temperature.