How is the rifling carved into the gun bore?

Use a steel bar slightly smaller than the inner diameter of the pistol, carve a groove at its specific position, and install a hard alloy steel sheet. There is one or two convex strips with a certain inclination on the steel sheet, the front end is beneficial to cutting, and the height of the convex can be adjusted. Pull a rifling position back and forth dozens of times, then cut a mother rifling, and then adjust the position to cut the next one. This method generally uses a single scraper to cut odd or even rifling, and can also use a double scraper to cut even rifling. You can also install a single scraper, a double scraper or three pairs of knives at opposite positions to cut 2 to 6 rifling lines at a time.

Hook broaching method

Put the hook knife on the steel pull rod slightly thinner than the diameter of the gun bore, and the height of the hook blade can be adjusted by manual woodworking broaching machine.

Screw in the tie rod layer for adjustment. Every time it passes through the barrel, the pull rod moves a few microns. With the uniform rotation of the barrel, the mother rifling with a certain degree of winding is drawn. After reaching the predetermined width, the second rifling is pulled at different positions. Early rifling guns only pulled rifling about 20 times, while better guns pulled the same rifling about 100 times. The more drawing times, the thinner and more accurate the drawing groove is. The early American colonists used hook broaching to make rifling, and the tools used were very simple hand-made wooden machinery, which the colonists could make themselves.

Broaching method of combined ring cutter

25-30 hard alloy steel rings are fixed on the pull rod, and the distance between each steel ring is equal. Each steel ring has the same number of equidistant scrapers as the mother rifling, and each cutter can be connected with the cutter on the next steel ring according to its winding angle, which can be regarded as a spiral line from beginning to end. The blade extension of each ring is slightly larger than that of the previous ring, forming a series of tools with stable width, depth and interval. This combined pull ring cutter can cut all the mother rifling lines through the gun bore at one time, which shortens the working time and improves the output and quality.

Top cone (or rifling punch) extrusion JE method

When a cemented carbide (such as tungsten carbide) pointed cone with the same cross-sectional shape as the inner cross-sectional shape of the wire hole passes through the barrel hole with an inner diameter slightly smaller than that of the pointed cone, the barrel metal passes through the barrel hole under the strong top pressure of the pointed cone, so that the inner diameter of the barrel hole is slightly increased, while the protrusions on the outer surface of the pointed cone squeeze through the inner wall of the barrel to form deformation, that is, the female rifling, and the concave part presses against the inner shadow along the barrel bore to form deformation, and the male rifling. Due to the high pressure, the metal density and hardness of the inner wall of the bore increase, and the process of reaming defects and rifling is completed. The inner wall of the hole becomes smooth due to the hard and smooth surface of the top cone. The service life of the bucket is doubled. This method was first invented by Germans and has been widely used in the production of gun barrels since 1970s. No matter which force method is used to make the rifling, under the microscope with large magnification, many cracks will be left in the groove, pointing in the direction of the scraper like a zigzag. Even after polishing to chromium plating, it can still be observed. However, the translation of the cutting process will produce random changes in the trenching distance, forming a stable feature. The material of barrel steel is not absolutely homogeneous, and the inner wall of the tube must be hard in some places, so the scraper processing will have different effects at this time. Metal fragments will have microscopic diameter changes and will be detected when they are launched: repeated marks will be produced on the soft metal of the warhead. That is to say, the top cone is polished to Mohs 8 by mechanical processing, which achieves mirror effect, and it also has its family characteristics (characteristics left by the same top cone), because there will be subtle differences between the top cones due to mechanical processing. And with the increase of shooting times. There will be random wear, corrosion spots and chemical gas corrosion traces, forming individual differences. In production, the factory will prepare more than two top cones on an extruder, which are usually used randomly and alternately, instead of a specific top cone extruding several barrel rifling at a time. A workshop will have multiple extruders running at the same time. Although a top cone can theoretically squeeze out the rifling of thousands of barrels, there will be subtle rifling differences in each batch of barrels. As long as it is enlarged to a sufficient multiple, its family characteristics can be distinguished.