Russian air rifle MP-512, which is popularly called "Murka", occupy a leading position in its class on the domestic market. Like many other Russian-made shotguns, it has some flaws. Most of them are eliminated with a simple file. Today we will learn how to improve the performance of the MP-512 rifle. The upgrade will relate to the most common, basic version of the weapon, as the modifications "Elegant" and "New Design" have their own personal characteristics.
a brief description of
Air MP-512 is produced since 1998. It has become popular due to its low price, relatively good performance, simplicity of the device and ease of upgrade. Another distinguishing feature of Murka is its large margin of safety, which also contributes to modernization. Among the shortcomings of weapons can be noted: instability of quality (each instance has its own problems), strong returns (especially after completion), unregulated descent. However, this is quite normal, considering how much the MP-512 costs. The price depends on the modification and materials of the bed. It ranges from 3-5 thousand rubles. The bed for MP-512 can be plastic or wooden. Naturally, wooden is more expensive. The sight for MP-512 is mounted on a dovetail. The rifle is mainly used for training and recreational shooting. It easily lends itself to modernization, which opens up the prospect of its use for hunting.
Main settings:
- Type of construction - spring-piston.
- The barrel is steel, rifled (6 rifling).
- Caliber - 4.5 mm.
- Type of bullets - lead.
- Weight - 2.8 kg.
- The number of charges is 1.
- Basic sighting devices - rear sight and front sight;
Well, now on to the modernization of the rifle. Let's start by increasing accuracy.
Platoon
Tuning MP-512 begins with the completion of the platoon. Due to the incorrect engagement angle of the rod and piston, the latter can lift the cylinder. The angle must be changed so that the thrust during cocking pushes the piston slightly down. Therefore, the hook plane must be rotated 5 degrees.
Soft descent
In order for the MP-512 gun to have a softer descent, you need:
- Correct the angle of the piston engagement with the sear.
- Correct the angle of the ledge of the trigger.
- Treat contact surfaces of the piston and the sear. It's about grinding and polishing.
- Treat the contact surfaces of the sear and trigger in the same way.
- Check the surface of the sear axis for burrs. If they are, you need to process the axis.
First of all, the engagement between the piston and the sear is corrected. For unprocessed rifles, the piston transfers the torque to the sear, a significant part of which is transmitted to the trigger. This needs to be fixed. A perpendicular is drawn to the sear, which must be shifted by 2-3 degrees to the side.
Then comes the finalization of the trigger (SK). On the factory rifle ledge SK has the wrong angle. The radius from the end of the step to the axis of rotation is greater than the radius from the base to the axis. This leads to the fact that when you click on the SK shooter acts on the sear in the direction of a larger hook with the piston, against the force of the spring. To solve this problem is very simple - you just need to level the shelf of the whisper. Processing begins with a file. Then you need to work with skins. And the final refinement is carried out using GOI paste. It should be noted that the edges of the descent must be sharp.
The manipulations described above lead to the fact that the pulling force drops from 2-3.5 kg declared in the passport to 0.4-0.5 kg.
Short descent
There are two ways to make the descent shorter. Firstly, you can put a transverse pin / screw, which will limit the movement of the trigger forward when cocking. In this case, the hook length of the ledge of the hook with the sear will decrease. Secondly, you can simply reduce the length of the ledge SK. The disadvantage of this method is its irreversibility.
Descent failure
Failure SK call it idle after the failure of a whisper. To get rid of the failure, you need to install a cylinder of a suitable size in the trigger spring. Usually use a piece of the rod from the gel pen.
Muzzle chamfer
Many shooters complain that the MP-512 airframe has a poor-quality factory facet of the muzzle end. As a result, the bullet at the time of the shot does not come off the rifling at the same time, which leads to a disruption of its trajectory. As practice shows, on the MP-512 guns, the upgrade of which we are considering, the bevel is not very beautiful, but even. Therefore, it is worth modifying it only if you are sure that it is necessary. Sometimes the manufacturer presses the barrel knurled under the fly. In this case, you have to cut the trunk, resume the chamfer, and sometimes even cut new threads.
For those who nevertheless decided to modify the muzzle face in their guns, consider one of the simplest methods for this crucial operation. So, to refine the muzzle face, we need:
- Trunk.
- Bullet.
- Vata.
- A ball with a diameter of 5-15 mm (a bearing is good).
- Abrasive of different fractions.
The first step is to fix the trunk in an upright position, with the barrel up. From the side of the muzzle cut in the trunk you need to stick first a bullet, then a piece of cotton. Vata is necessary so that the abrasive does not fall into the main part of the barrel. Then a little abrasive is poured into the barrel, so that a small slide forms. A ball is laid on it. It is desirable that it be steel. Now, a bevel is made with rotational movements with light pressure. Rolling along the muzzle, the ball removes excess metal from the abrasive. After some time, you will see how the chamfer takes on a more correct shape. It remains only to push the bullet with cotton from the barrel and clean it several times with new cotton.
The rotation of the ball can be done either manually or using a drill. To do this, you need a tube like a rod from the handle.
Muzzle
For a more accurate and balanced shooting, guns are often heavier using a muzzle, and the MP-512 pneumatics is no exception. The weight of the muzzle can range from 300 to 400 grams. He is selected experimentally - different muzzle covers are put on the gun until a good balance can be achieved. It is desirable that in the end the weight of the rifle does not exceed 3.5 kg.
This is where we finish operations to increase the accuracy of the rifle. If everything is done correctly, then using the tips described above, you can bring the accuracy of firing to 10 mm from a distance of 25 m. The MP-512 tuning is not finished yet, because you also need to take care of its power.
Boring back
The backdrop in this case is called the trigger block. To strengthen the MP-512 spring (put a more powerful and longer one), you need to increase the recess in the back to about 30 mm. It is important that after this operation the bottom remains flat. Boring is made by a mill. If in your arsenal there is only a drill with a tip angle of 120 degrees, then under the spring you will need to put something like a flat washer. A coin is a good fit for these purposes. You can not bore the backdrop under a new spring, but then it will have to be trimmed.
Piston weighting
The piston of a rifle usually needs additional weighting. For this, a weighting agent is simply installed in it. The latter should weigh about the 150 bullets you shoot. The weighting agent can be purchased on the Internet or ordered from a turner. The MP-512 rifle sometimes has a special protrusion at the bottom of the piston that eliminates the unevenness of the spring (no matter how neatly the spring is cut off, the last turn protrudes). Due to the protrusion at the bottom of the piston after installing the weighting material, skew may occur, which negatively affects the operation of the rifle. Therefore, if such a protrusion is found in your weapon before installing a weighting agent, it must be eliminated.
There are three ways to do this. The right option is the easiest - buy a piston without a protrusion. Its price is about 250-300 rubles. The second option is more difficult - to grind the protrusion on a lathe. The third option is the most unusual - on the bottom of the piston on a bituminous or any other thick mastic you need to glue the washer, which will align the bottom. The weighting agent will clamp it, and the mastic will firmly fix. A coin of a suitable size can act as a washer.
A spring working with a piston, on the bottom of which there is a protrusion, is usually deformed. It needs to be aligned. You can do this with a simple file. The ends of the spring must be sharpened so that they become flat. It is advisable to do the same from the other end of the spring, which abuts against the trigger block.
Bypass hole
For better rifle performance, the diameter of the bypass hole is reduced. This is done using a special sleeve. It is inserted into the rubber bypass pad. The sleeve, like the weighting compound, can be bought or ordered from a turner. To reduce the diameter of the bypass hole, a piece of the rod of the gel pen is also used. To prevent the air flow from pushing it out, a hat should be made from one end.
Cuff
Tuning MP-512 also involves the refinement of the cuff. Before talking about how this is done, it is worth recalling the theoretical aspect of her work. The cuff has static and dynamic friction. The first thing we feel is moving her hands. And the second occurs during the shot when the cuff is bursting with pressure. The latter phenomenon is called obturation.
Because of the obturation, the process of the shot is inhibited, so the groove is poured. However, a small obturation is still necessary, as it enhances compaction and contributes to less air loss, which leads to increased compression.
Thus, our task is to reduce dynamic friction to a minimum, without compromising compression. The lower the compression, the higher the peak pressure, which at the moment of gas exposure to the bullet drops, which leads to a loss of the bullet’s flight speed. And if the dynamic friction of the cuff is too high, then part of the spring’s energy is lost, just like the pressure in the compressor, which also leads to a loss of speed. So that everything works well, you need to find a middle ground.
It is worth noting that if the piston and the cuff fall into the cylinder, this does not mean that the compression will be weak. After all, during the shot the very obturation contributes to the compaction of the system. Also, do not worry about the fact that the compression lasts no more than 10 seconds - this is quite enough.
Checking compression is pretty simple. Between the bypass and the breech, you need to hold a rectangular plastic liner. If everything is in order, then during the shot the piston will not touch the bottom of the cylinder, and when opening the barrel there will be a characteristic clap. If hissing is heard during the shot, then the bypass is leaking.
Now you can start filling the cuff. The first thing to do is trim the barbs, if any. After that, the front of the cuff groove is covered with sealant. Here you need to make sure that no air bubbles form. Then you need to wipe the excess sealant with a cloth and slide your finger along the seam to form a shallow groove. It should have a semicircular profile and be no deeper than 1 mm. Then the back groove is smeared to the top. Now you can put the cuff on the piston, insert the piston into the cylinder and leave it all for 12 hours to dry. The second cuff is poured and dried separately. In the front groove of the third, you need to put an elastic band for money before pouring. The result is 3 cuffs with different diameters and static friction. At the same time, they have no dead volume, and dynamic friction is much less than before tuning.
When the cuffs have dried, you can begin the assembly process. The piston and cuff should be slightly lubricated. It is important to ensure that the grease does not get on the front of the cuff. The weighting agent is put in place, and everything is carefully assembled. Now you need to check with which cuff the rifle will shoot better. A chronograph is needed here.
Breech
The breech of the "fresh" rifle smoothly goes into the rifling, which entails a slight effort of moving the bullet. It can be fixed.
First of all, you need to grind ingots under the standard thread of the barrel. Then, instead of the crossbar (the wedge that holds the barrel closed), the shank of a 9 mm drill is placed. Having fixed the ingot, you need to hit the drill with a heavy hammer. Due to this, the trunk should go beyond the coupling by one and a half to two centimeters.
Then you need to saw off the protruding part and use the wide flat file to straighten the breech. Periodically, you need to attach the barrel to check the position of the coupling relative to the compressor. Then, after wrapping the 600th skin on the file, you need to grind all the bumps. If desired, you can repeat the procedure with the 1000th skin. Since the trunk after the described manipulations will move, you will need to re-make a groove under the axis of the barrel. The state chamfer will also have to be renewed. It is done in the same way as the muzzle.
Conclusion
Today we figured out how to make tuning the MP-512. After the described operations, aimed at increasing the accuracy and power of the rifle, you can do more fine-tuning.
Adhering to the above recommendations, you can quite significantly improve the performance of the rifle. If everything is done correctly, its power can reach 20 J, and accuracy of 10-20 mm from a distance of 25 m. With such indicators, you can feel confident both when training at targets and when hunting from a distance of up to 50 meters.
The MP-512 rifle, the price of which is really pleasing, after an upgrade becomes a completely different weapon. She is devoid of "childhood illnesses" such as poor balance, poor descent and constant vibrations. The accuracy and power of the MP-512 (bullet speed ranges from 250-280 m / s) allows the rifle to compete with more expensive counterparts.