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 Marushin MP40 (abs)... Basic Parts Inspection Guide

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Cerwyn
Cerwyn (Site Admin)
Cerwyn (Site Admin)
Cerwyn


Number of posts : 11071
Age : 65
Location / Country : North Wales
Registration date : 2008-07-20

Marushin MP40 (abs)... Basic Parts Inspection Guide Empty
PostSubject: Marushin MP40 (abs)... Basic Parts Inspection Guide   Marushin MP40 (abs)... Basic Parts Inspection Guide Icon_minitimeTue Aug 05, 2008 9:56 am

Basic Parts Inspection Guide... Marushin MP40 (ABS)

Marushin MP40 (abs)... Basic Parts Inspection Guide MP40Montage

Field Stripping and Cleaning have already been covered in previous Step by Step Guides so this guide begins with your MP40 already stripped into its component parts.

Re-assembly is explained in a separate Guide
.


1. Detonator Pin and Chamber.

Marushin MP40 (abs)... Basic Parts Inspection Guide Mp40DetPin

The metal Detonator Pin can be prone to corrosion damage and occasionally being knocked out of shape by miss fed cartridges.


Light corrosion can be removed with Wire Wool and / or Emery paper (Wet’n’\Dry)

The Chamber is moulded in ABS and will wear out in time. Below is a photo of a well used and new chamber side by side for comparison.

Marushin MP40 (abs)... Basic Parts Inspection Guide MP40DETCHAMBERSNEWOLD

Check the base of the chamber to ensure the locating hole for the Pin is undamaged.

Marushin MP40 (abs)... Basic Parts Inspection Guide MP40CheckDetpinlocationrear

Check the entrance into the Chamber for damage.

Marushin MP40 (abs)... Basic Parts Inspection Guide Mp40checkinsideDetChamber-1

Any rough edges here might interfere with your cartridges feeding into place. Any light nicks and burrs can be carefully smoothed out by a sharp blade or abrasive paper.
Check the inside of the chamber for dirt and deposits. Build up of dirt or gummed up old oil will cause cartridges to stick and jam inside

2. Receiver Tubes... Upper & Lower


Both receiver halves are locked together at 3 points.

First point being by "bayonet fixing" type lugs around the outside of the Upper Receiver and inside the end-cap's ring of the Lower receiver

Upper Receiver lugs...

Marushin MP40 (abs)... Basic Parts Inspection Guide MP40LugsUpperReceiver

Marushin MP40 (abs)... Basic Parts Inspection Guide MP40Lugpartway

Lower Receiver Lugs... (note receiver stripped bare for clarity)

Marushin MP40 (abs)... Basic Parts Inspection Guide MP40InternalLug

Second point is the spring loaded take down pin that locates in a drilled hole on the underside of the upper receiver tube.

Marushin MP40 (abs)... Basic Parts Inspection Guide BoltandRecoilTuberemoved-1

The spring loaded take-down pin is a snug fit in it's hole cut into the underside of the receiver tube. Being abs, the edges of this hole are easily damaged. Any elongation of the hole can cause the receiver tube to move back and forth during firing...



Third point is the slot cut into the back of the magazine well...



Marushin MP40 (abs)... Basic Parts Inspection Guide MP40Magwellslotparthome
Marushin MP40 (abs)... Basic Parts Inspection Guide MP40Magwellslotlockedhome

Check that these bayonet fixing lugs are not worn or damaged. Any wear at these points could fail to lock the receiver tubes together causing the gun to seperate during firing.

It is possible that worn lugs caused this dramatic failure:-

https://mp40modelguns.forumotion.net/modelgun-videos-f2/marushin-mp40-falling-to-bits-posted-by-claymore-t59.htm


3. Bolt and Extractor

Bolt condition is vital to the firing performance of your model gun.
Starting at the bolt face, this photo shows a well used and a new example for comparison.


Marushin MP40 (abs)... Basic Parts Inspection Guide MP40Boltfacesnewoldlarge


The Bolt strips each round from the magazine as it travels forwards. The two protruding “prongs” for want of a better term ( ! ) seen here directly above the circular recess in the bolt face centre, scoops the round up and pushes it forwards towards the Detonator Chamber.
As this is the first point of contact, any wear or chips to the “prongs” can result in miss feeds and a non firing gun. Notice how the older bolt’s (on the right of the photo) prongs have already been partly flattened through wear.

The round is pushed home into the Detonator Chamber and its’ rim settles in the circular recess in the Bolt Face Centre.
These photos show how the round is held. You can see the three means of securing the round…


Marushin MP40 (abs)... Basic Parts Inspection Guide MP40Roundheldinbolt1-1

Marushin MP40 (abs)... Basic Parts Inspection Guide MP40Roundheldinbolt2-1

i.e. Circular Recess, Extractor Claw and the prongs…
Any wear or chips to the recess edges can result in cartridges dropping off the bolt prematurely. If any of these 3 are damaged the cartridge will more than likely drop off the bolt. Generally this results in rounds firing, but failing to extract and eject cleanly from the chamber and port.



The extractor claw is spring loaded and clips over the cartridge rim to hold it securely.
Check that the Extractor pivots smoothly against spring pressure…


Marushin MP40 (abs)... Basic Parts Inspection Guide MP40Wipedownextractor

Check the extractor’s claw for dents or chips. Any slight dents can be cleaned up by careful use of a fine file. Aim to get a sharp and even edge to the claw.


Check the groove underneath the Bolt that rests against the Sear when the gun is Cocked. Wear here may result in the bolt releasing too early, i.e. before the trigger is pulled or failure to Cock securely.

4. Bolt Carrier and Cocking handle.

Check the cocking handle’s safety toggle for smooth and secure movement.
Ensure the outer diameter of the Carrier is free from burrs and dirt. This part slides against the inside of the Receiver tube so must be smooth.

5. Trigger and Sear.

The Sear moves down into the Lower Receiver when the trigger is squeezed. Ensure it drops into it’s recess cleanly and that it returns smoothly when the trigger is released. Problems here may lead to the gun firing accidentally and uncontrollably or the bolt refusing to move forward when the trigger is pulled.



Cerwyn
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Cerwyn
Cerwyn (Site Admin)
Cerwyn (Site Admin)
Cerwyn


Number of posts : 11071
Age : 65
Location / Country : North Wales
Registration date : 2008-07-20

Marushin MP40 (abs)... Basic Parts Inspection Guide Empty
PostSubject: Re: Marushin MP40 (abs)... Basic Parts Inspection Guide   Marushin MP40 (abs)... Basic Parts Inspection Guide Icon_minitimeMon Sep 22, 2008 3:16 pm

Details Updated

Cerwyn
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