Semi-automatic shotgun MP-155 has established itself as a reliable tool for hunting and sports, but even the most advanced mechanics require periodic maintenance. Regular cleaning and lubrication of components is not just a formality, but a necessity that extends the life of the barrel and mechanisms. Owners often encounter difficulties during first dismantling, not knowing how to properly remove the forend or separate the barrel so as not to damage the seals.
Incorrect assembly can lead to wobbling, automatic reloading failures, or, worst of all, injury when firing. It is important to understand that disassembly MP-155 has its own technological features that distinguish it from classic pump-action systems or foreign analogues. In this article we will analyze in detail the process of complete and partial disassembly, paying attention to the critical points of assembly.
Knowing the structure of your weapon allows you not only to keep it in perfect condition, but also to quickly eliminate minor malfunctions in the field. We will look at the key aspects of working with the bolt group, recoil spring and gas system. Remember: complete disassembly of the trigger mechanism (trigger mechanism) at home unless necessary is strictly not recommended.
Partial disassembly: preparation and removal of attachments
Before starting any manipulations, make sure that the weapon is unloaded. This is a basic safety rule that cannot be violated. Remove the cartridge from the chamber, lower the magazine and pull the bolt several times, visually checking that there is no ammunition in the barrel. To work, you will need a minimum set of tools, usually included in the package or available to every hunter.
The process of partial disassembly begins with the separation of the forend. On MP-155 it is secured with a screw located in front of the under-barrel magazine. Unscrew this screw counterclockwise using a coin or slotted screwdriver. After loosening the lock, slide the forend forward and remove it from the guide. Be careful not to lose the magazine follower spring if it is not structurally secured.
The next step is to disconnect the barrel from the receiver. To do this, you need to unscrew the under-barrel magazine. While holding the barrel with one hand, rotate the magazine tube counterclockwise with the other. Once the threads are disengaged, the barrel can be removed using an upward and forward motion. At this stage, the main cleaning mechanism is already available.
- 🔧 Unscrew the screw securing the forend and remove it moving forward.
- 🔧 Unscrew the magazine tube to release the barrel.
- 🔧 Remove the barrel by lifting it up from the receiver.
- 🔧 Remove the bolt group by pulling the bolt back all the way.
☑️ Checklist before disassembly
It is worth noting that on some modifications MP-155 with magnum chambers there may be nuances in the length of the return spring, but the algorithm of actions remains the same. When removing the barrel, pay attention to the condition of the gas chamber sealing ring - it is this that most often suffers from careless handling.
Detailed disassembly of the bolt group and gas system
Bolt group MP-155 - This is the heart of the gun’s automation. To remove it, move the bolt to the rearmost position and remove it through the receiver window. Inside the bolt there is a firing pin and a striker spring. To dismantle them, you need to press the pin that secures the striker and carefully remove it. Caution is important here: the parts are small and can fly apart if moved carelessly.
The MP-155 gas system is built on the piston principle. The piston is located around the under-barrel magazine. To remove it after removing the barrel and fore-end, you just need to remove the piston from the guide. Piston rings require special attention when cleaning, since carbon deposits accumulating on them can lead to jamming of the automation.
It is important to orient the parts correctly when reassembling. A wrong side of the piston or an incorrectly installed firing pin will cause the mechanism to fail. When disassembling the bolt, pay attention to the ejector - it is spring-loaded and requires care when cleaning. Do not use excessive force to avoid breaking the thin walls of the bolt slot.
⚠️ Attention: When removing the firing pin from the bolt, hold it with your finger. The firing pin spring is under tension and can fly out with force, becoming lost in the grass or floor.
The gas chamber in the receiver also requires regular cleaning. Carbon deposits formed during the combustion of powder gases create an abrasive mixture that accelerates wear of rubbing surfaces. Use special brushes and solvents to remove solid deposits. Do not scratch the shutter mirror and bore with metal brushes.
Nuances of the MP-155 gas system
The MP-155 gas system has a self-compensating mechanism, but it is sensitive to the quality of the cartridges. The use of weak charges can lead to the shutter not firing, and overly powerful ones can lead to the bolt hitting the frame. The amount of gases is adjusted by changing the diameter of the gas outlet hole, but in the factory this is done by selecting a piston.
Disassembly and maintenance of the return mechanism
Return mechanism in MP-155 consists of a rod, a return spring and a buffer washer. The rod is inserted into the tube of the under-barrel magazine. During disassembly, it is removed after removing the barrel. Often hunters are faced with the problem of “drying out” or deformation of the plastic buffer washer (damper), which leads to strong shocks to the shutter during idle release.
Check the condition of the spring. It should not have traces of corrosion or residual deformation of the turns. If the spring is stretched, the bolt will not reach its full forward position, causing delays in feeding a round from the magazine. Replacing the spring is a simple operation that requires no special tools other than pliers to secure it if necessary.
When assembling the recoil mechanism, make sure that the rod is seated correctly in the receiver socket. Incorrect installation can lead to misalignment and jamming of the bolt during the first shots. Lubricate the rod with a thin layer of gun oil, but do not overdo it so that the oil does not get into the bore in large quantities.
- 🔍 Inspect the plastic washer for cracks and wear.
- 🔍 Check the spring coils for corrosion and deformation.
- 🔍 Make sure the inner surface of the magazine tube is clean.
- 🔍 Apply a thin layer of lubricant to the rubbing surfaces of the rod.
Often problems with chambering a cartridge are associated precisely with the weakening of the return spring or contamination of its channel. Regular preventive maintenance allows you to avoid most breakdowns at the most inopportune moment during the hunt. Remember that edged weapons require a “warm” attitude.
To extend the life of the plastic buffer washer, lubricate it with silicone lubricant, which does not destroy the plastic, unlike some harsh gun oils.
Assembly of MP-155: step-by-step algorithm of actions
Assembly MP-155 done in the reverse order of disassembly. Start by installing the return mechanism. Insert the rod with the spring into the tube of the under-barrel magazine. Make sure it moves freely and does not bind. This is the foundation on which the operation of all automation is based.
Next, install the barrel. Align the holes in the barrel with the threads of the receiver and begin screwing the magazine tube clockwise. Do not over-tighten the thread “all the way” right away - first tighten it by hand, then tighten it. The threads on the MP-155 are of high quality, but careful handling will extend its life.
After fixing the barrel, install the forend. Slide it onto the guides and tighten the fixing screw. Check the fit of the forend - it should not be loose, but it should not require a vice for installation. The final stage is installation of the bolt group. Insert the bolt into the receiver and push it forward. The dispenser should snap into place, locking the bolt.
| Assembly stage | Key Action | Checkpoint |
|---|---|---|
| Return mechanism | Installing the rod into the tube | Free movement without jamming |
| Barrel group | Winding up the store | Tight fit without play |
| Bolt group | Inserting the gate into the box | Operation of the cut-off reflector |
| Check | Idling (with caution) | Clear click, automatic operation |
After assembly, be sure to check the operation of the mechanism. Tighten the bolt several times, make sure that the magazine cut-off and the spent cartridge deflector are working. If you feel delays or unusual resistance, disassembly will have to be repeated to identify the error. Haste during assembly is the main enemy of a quality result.
Troubleshooting Common Assembly Problems
One of the common problems after assembly is that the cartridge is underfilled. The bolt does not reach the end, and the cartridge remains in the magazine or becomes distorted. Most often, the reason lies in incorrect installation of the return spring or contamination of the barrel bore and patina. It is also worth checking whether the gas system piston is stuck across.
Another common mistake is incorrect installation of the firing pin in the bolt. If it is skewed, the firing pin will not reach the primer, or, conversely, will pierce it through, which is dangerous. When assembling the shutter, make sure that all parts fit into place without being forced. The mechanism should be assembled easily, with the help of your fingers (except for screws).
⚠️ Attention: If, after assembly, the trigger does not fire (if there is a cartridge), stop using the weapon immediately. Check the installation of the striker and the integrity of the spring. Shooting with a faulty trigger mechanism is dangerous.
Delays in ejecting a cartridge case are often due to contamination of the chamber or wear of the ejector claw. When reassembling, make sure the ejector spring is intact and installed correctly. B MP-155 The ejector is located in the bolt, and replacing it requires care. Be careful not to lose the small spring and pin.
90% of problems with the MP-155 automation after cleaning are solved by correctly installing the gas system piston and checking the length of the return spring.
Lubrication and preservation: the final stage of maintenance
Correct lubricant - the key to long life of mechanisms. Modern weapon oils that can operate in a wide temperature range are suitable for MP-155. In winter, use more liquid formulations, in summer - viscous ones. Pay special attention to the friction surfaces of the shutter and the return spring rod.
Do not over-lubricate the bore and chamber before firing. Excess oil can create excess pressure when firing or, conversely, lead to under-action of the bolt due to the hydraulic effect (oil wedge). A light film is enough to protect against corrosion. After the hunt, remaining oil and soot must be removed.
When preserving weapons for long-term storage, lubricate all metal surfaces with preservation lubricant. Treat wooden parts (forend, butt) with special compounds for wood to avoid drying out or swelling. Store the gun in a dry place, preferably in an upright position or on special stands, so as not to deform the barrel.
- 🛢️ Use synthetic oils for low temperatures in winter.
- 🛢️ Remove excess lubricant from the barrel bore before shooting.
- 🛢️ Treat wooden parts with special impregnations.
- 🛢️ Check the condition of the rubber seals every time you clean them.
Regular Maintenance MP-155 does not require complex skills, but requires attentiveness and accuracy. By following these simple rules, you will ensure reliable operation of your gun for many years. Remember that weapons do not forgive negligence, but generously reward for careful use.
Is it necessary to disassemble the trigger for cleaning?
In most cases, complete disassembly of the trigger mechanism (trigger mechanism) is not required and is not even recommended unless absolutely necessary. The mechanism is assembled in a closed case, and dirt getting inside is minimal. Cleaning the outside and blowing with compressed air is usually sufficient. Interfering with the internal mechanics of the trigger can disrupt the factory settings and lead to failure.
Which oil is best to use for MP-155?
The optimal choice is specialized gun oils, such as "Ballistol", "Hoppe's No.9" or domestic analogues (Gun oil). It is important that the oil does not harden in cold temperatures if you plan to hunt in the winter. Automotive oils (WD-40, motor oils) are not recommended, as they can destroy some types of plastic and rubber used in the structure.
Why is the shutter tight after assembly?
Difficult movement of the shutter after assembly can be caused by several reasons: misalignment of the return spring, dirt getting into the guides, improper assembly of the gas system, or the use of too thick lubricant in the cold. It is also possible that during assembly an error was made in the sequence of installation of the bolt group parts.