Procedures for Field Stripping and Cleaning your CZ 858

Maintenance on your CZ 858 may seem complicated but it’s really not as hard as it looks. This article is written to alleviate any confusion when it comes to disassembly and maintenance of the CZ 858.



MAINTENANCE INSTRUCTIONS

Stripping for Cleaning – Disassembly
 
1. Point your rifle in a safe direction and check that it is unloaded!
2. Remove the magazine
3. Point in safe direction and pull trigger. You must trip the striker (dry fire) before you can remove and reassemble the bolt.
4. Grasp the rifle by the receiver from below and using your right hand thumb depress from the left side the protruding end of receiver cover pin. Then grasp by the right-hand thumb and index finger the knurled head of the pin and pull the pin out to the right until an audible click is heard.
5. Place the right hand thumb against the rear wall of receiver cover. Using the right-hand thumb forward and upward pressure slide the return mechanism out from the receiver (Figure 6). Grasp the receiver cover and pulling it to the rear remove the whole return mechanism out from the rifle.



6. Using cocking handle retract the bolt to the rear up to stop and then lift it up slightly. Once the front part of the bolt is sufficiently lifted up above the receiver place the right-hand fingers under the bolt gripping the bolt in the palm and take it out from the receiver.
7. Take the bolt into your left hand and grasp the striker-hammer by the head. Rotate the hammer-striker counterclockwise and withdraw to the rear from the breech block carrier (Figure 7). Projection in the bolt breech carrier must go through cross groove into adjoining concomitant groove at the striker.
8. Retract the breech block to the rear and take it out from carrier in downward direction (Figure 8).
9. Remove the bolt lock from the breech block by tilting it upwards (Figure 9).
10. Employing the right-hand thumb press from the left side projecting part of the handguard pin. Then grasp by right-hand thumb and index finger the knurled head of the pin and pull the pin out to the right until an audible click is heard.
11. Using your right-hand remove handguard by lifting up its rear portion and withdrawing it to the rear.
12. Using your left-hand grasp the rifle from below by the fore-end. Grasp the piston with your right hand and press it rearward against the force of piston’s return spring. Then tilt the piston upwards away from piston cylinder and pull the piston out by pulling it at an angle forwards sliding it out from the opening at the rear sight base (Figure 10). If the piston spring has not been shifted out together with the piston, remove it at the direction of the piston’s rear end.



CAUTION: No further disassembly is needed for routine maintenance and preserving. Never attempt to disassemble your semi-automatic rifle further. If you assume that your rifle requires adjustment or repair, then entrust this task to a competent gunsmith.

Assembling the Rifle

1. Using your left-hand grasp the rifle from below by the fore-end. Grasp the piston with the slipped-over spring and insert its cylindrical part downwards up to stop into opening of the rear sight base. Tilt the piston head to the cylindrical seat of the gas cylinder and release the piston. Under the spring pressure the piston will be shifted to its front position.
2. Make the tips of handguard front joiner snap in the grooves on the gas adapter and tilt the handguard down. Insert handguard pin completely to the left thus securing handguard against any inadvertent release.
3. Place the breech lock into seating at the breech block. Put the breech block in recess sited at breech block carrier near the bridge, whereupon shift it forwards to engage the grooves in the carrier. Shift the striker-hammer partially in the breech block carrier so that the witness marks on the striker-hammer and the rear wall of the breech block carrier are oriented opposite to each other (Figure 11). Then turn the striker-hammer by the full length of the witness mark to the right and insert it into striker-hammer carrier up to stop.
4. Grasp the assembled bolt by the right hand with thumb placed against the rear face of breech block carrier and the middle finger against the front face. Using left hand hold the rifle from below by the receiver with muzzle slightly inclined to the ground. Insert the bolt from above in the rear part of the receiver. Slide the inserted bolt as far as the extreme front position, whereby the striker-hammer remains retained by the left-hand catch of striker (Figure 12).
5. First of all, insert the striker-hammer spring (operating spring) partially in the cavity of striker and then the return spring in the opening of breech block carrier (Figure 13). Shift the safety lever to position 1” and squeeze the trigger. This releases the striker-hammer from the left-hand catch and return mechanism can be moved forwards without any resistance. Pull the front part of the cover under to engage the grooves in the carrier and by pushing forwards and downwards slide the projection of base in the recess in the rear part of the receiver (Figure 14). Subsequently lock the return mechanism by inserting receiver cover pin until an audible click is heard. If the striker-hammer is not released by squeezing the trigger then it means that the breech block carrier is not in the extreme front position and the striker is held by the right hand catch.

Assembled Rifle Inspection

When inspecting assembled rifle it is necessary to check:
- Function of the bolt
- Function of the trigger unit
- Correctness of the rear sight and front sight
- Function of the shoulder rest



Cleaning the Rifle

Clean the rifle

- Each time you use it
- If you get your automatic rifle wet
- As soon as possible after shooting
- Immediately after shooting corrosive ammunition
- At least once a year in a temperate climate
- As often as once a month in a tropical climate, or other demanding weather environments

Cleaning and Materials Used

- Clean fine cloth/swab suitable for cleaning and lubricating of parts and components
- cleaning patch (only for barrel bore cleaning)
- light gun oil
- Hairbrush (included with accessories)

Cleaning the Barrel Bore and the Cartridge Chamber

The barrel bore shall be cleaned from the side of the muzzle. For doing this it is necessary to screw both parts of cleaning rod and oakum holder together (Figure 15). Slide the muzzle protection over cleaning rod. Insert the cleaning rod end with annular groove into longitudinal opening of at the unscrewed oil-can plug and secure it with front sight wrench, which is put through transversal opening in the oil-can plug. Wind a cleaning patch round the oakum holder so that it could pass through the bore with a slight resistance in order that it fills the grooves well. Then immerse the patch into preserving oil, and insert into the barrel bore from the direction of muzzle. Slide muzzle cap over muzzle thread protector and rotate in such a way that the muzzle thread protector lock is engaged in cut-out of the muzzle cap.

Grasp the cleaning rod by the front sight wrench and plug and push-pull the cleaning rod with its attachment continuously without any undue force seven or ten times through the whole length of the bore. After this remove the muzzle cap, pull the cleaning rod out and replace the patch; dip it again in the cleaning agent and again draw several times the cleaning rod through the bore. Then clean the cleaning rod of preserving oil and put through the cut in the oakum holder a clean cloth. Repeat cleaning with the cloth a few time if the cloth shows some spots from corrosion, powder residues or fowling. If these spots appear even when the barrel bore has been wiped for several times then it is necessary to repeat cleaning with a patch and preserving oil, and afterwards again using the clean cloth/patches wipe the barrel bore dry. When the last cloth comes out without any traces showing residues of fouling or corrosion then clean the cartridge chamber.

For cartridge chamber and piston cylinder cleaning the patch is screwed into the transverse opening of the oil-can plug from the threadless side of the opening. The cartridge chamber is then cleaned in the same way as the barrel bore, at which the oil-can when in vertical position serves as patch holder handle.

Cleaning of Other Rifle Parts

Piston cylinder is wiped with a patch soaked with preserving oil and then wiped dry. Perform cleaning procedure till all firing residues and/or fouling are removed. Piston cylinder is wiped dry and then preserved by applying a thin film of preserving oil. When cleaning the piston, it is necessary to pay attention to removing fouling or other deposits from the circumferential groove on its head. After washing over in cleaning agent the piston shall be wiped with a patch. The piston with fouling and deposits removed should be wiped by using a dry cloth and subsequently preserved by applying a light layer of preserving oil.

Receiver, bolt and the non-disassembled trigger unit, rear sight and return mechanism shall be cleaned using wooden sticks with wound up cloth damp with preserving oil. Openings, grooves, cut-outs and recesses are cleaned using pointed wood sticks. After cleaning the parts and components they should be wiped dry using a clean cloth and preserving oil. It should be checked after cleaning the trigger that the reassembled trigger unit parts are positioned correct, especially the trigger unit spring legs.
Parts heavily fouled or dirty with powder combustion residues should be immersed into preserving oil for 30 minutes maximum. Preserving oil remains should be carefully removed.

The wooden parts of the rifle, ie. The stock, piston grip and forend, should be wiped with a lightly oiled cloth and wiped dry with clean, dry cloth. From time to time apply light layer of wood oil.

Preserving

 Preserving Material Used

- light gun oil
- Wood or linseed oil to infuse wood parts of the firearm

Before beginning the barrel bore and cartridge chamber preservation pull a cloth soaked with preserving oil through cut-out in the patch holder. The cloth must be of such a size so as to pass through the bore snugly. Push-pull the cleaning rod with attachment two or three times through the entire length of the bore so that the preserving agent is well adhered to the grooves and lands of the bore and cartridge chamber and forms a thin continuous layer. Excessively greased parts collect dirt very rapidly and for this reason it is necessary to apply only a fine layer of preserving agent using a grease soaked cloth. When lubricating recesses, grooves and slots it is necessary to roll the cloth round a wooden stick.