This invention relates to a method of straightening the metal barrel of a weapon.

The metal barrels of weapon, such as guns and shot-guns are usually made in the following manner. A hole is drilled in a metal rod and thereafter the rod is cold- forged by stretching it to the final length, which results in an absolutely straight barrel material. After this the outside of the barrel is turned to final form, and in this working period in the barrel often arises heat tensions, which causes a straight barrel to curve. In the barrel arising defects in this working period are frequent, next every second of manufactured barrels is discarded or is straightened.

In the known methods the straightening is made by a cam press, but its use is adapted to only proportionately thick gun barrels and it cannot be used in shot-gun barrels, so they cannot be straightened by the methods nowadays.

By using of different kinds of weapon at same time there can arise different kinds of curvatures on the barrels, when the barrel push against something or when the barrel becomes properly squeezed. Even repairing of these defects is difficult or impossible to do with the methods nowadays.

Metals are crystallized materials and a good picture of the atomic construction of the metal crystals may be had, if you think the crystal as being shaped by posi- tive ions to a space lattice, between which the open¬ ings are filled with negative charged electrons shaped as an electron cloud. These is kept together by several cohesion forces, which are established between the

negative charged electron cloud and the positive ions working electric power of attraction.

Depending on the above showed construction of the metal binding, the cohesion force has no direction or is at least very weak. This is also showed by the fact that the atoms groups together in the metal, that the number of their nearest on the same distance situated neigh¬ bours or coordination number becomes as large as possi- ble.

Every system or any wished particle left for itself will find balance, which is characteristic, that the free energy of the system has minimun worth at constant pressure and constant temperature. The material of the barrel is as usual essentially in this condition, when it is stretched to its final measure by cold-forging.

After this the barrel is worked or the outside is turned. Seldom this is done so homogeneously through the material, that there between its different parts will not be left forces, which often are unfavourable. They make the metal corrosion ready and as above is mentioned, the rest forces also signify prestressing and in unsymmetrical working they cause winding. In this way a straight barrel material becomes faults during working. The effects of rest forces can be re¬ duced by a little addition working for example straight¬ ening or 0,5 percent stretching, which essentially homogenizes the stress condition. On the other side, as it is above mentioned, at least the barrel of the shot¬ gun does not last out mechanical straightening and generally different kinds of complicated, known methods of removing the rest forces course the production re- markable additional costs and with these received re¬ sult is often unfavourable.

The purpose of the invention is to clear away the above mentioned drawbacks. Especially the purpose of the invention is to show a new method, which helps the barrel of different kinds of weapon can be rapidly and simply straightened.

The characteristics of the invention are showed in the claims.

In the method according to the invention for straighten¬ ing the metal barrel of a weapon an elastic blow or such a blow is turned to the barrel, which blow does not course mechanical changes or disadvantage on the surface of the barrel. This elastic blow makes the crystal construction of the metal barrel to vibrate so that the tensions, which are produced to the crystal construction will be eliminated and the crystal con¬ struction will take form of essentially balance, which corresponds to the straight position of the barrel, which it had for example before the turning of the outside of the barrel. In a corresponding way as it is mentioned above, where tensions coursed by heat are eliminated can also by mechanical influence coursed tensions on the barrel be eliminated.

Preferably the blow according the invention is directed on the barrel essentially in its cross direction, for instance on its other end and on the end preferably in the direction, in which the blow already itself straightens the barrel.

The strength of the blow, which is used, naturally var¬ ies depending on the size of the defect and the materi¬ al and the thickness of the barrel. Preferably the direction and the size of the blow is selected so, that it course the metal crystal construction of the barrel to move to balance position, as possible over the bal-

ance position, when the elastic construction courses the crystal construction to vibrate and to find the minimum energy corresponding balance position.

Preferably the blow is produced by beating the barrel against an elastic piece, which may be for instance sufficiently stiff and elastic rubber, plastic or corre¬ sponding material.

So the method according to the invention make it possi¬ ble to remove from the metal barrel of a weapon during the work appeared heat tensions and also different kinds of mechanical tensions, which without removing make the barrel incorrect and unusuable.

The straightenning method according to the invention can be used extraordinarily to straighten the barrels of both gun or shot-gun and it is aslo adapted to be used to straighten the barrels of other kind of weapon. In this way different kinds of solutions of the inven¬ tion are possible in regard to the invention idea re¬ stricted by the claims.