Marushin XM177E2 kit - first time assembly

22 - front sight
Assembling front sight with a piece of barrel



Parts:
A#4 - pin
X#74 - barrel section
A#140 - sling loop
#173 - flash hider
#175 - front sight



Work:
Put front sight (#175) on piece of wood, insert sling loop (A#140) into its place.
Insert pin (A#4) into the hole, hammer it in.
Screw flash hider (#173) ono barrel section (X#74).
Screw barrel section into front sight (near vertical side).

Verify:
Parts are held firmly. Use Loctite to make this more permanent.

23 - barrel
Remaining barrel parts.



Parts:
A#8 - front foregrip catch
#9 - barrel section
A#12 - barrel nut



Work:
Put front foregrip catch (A#8 ) onto barrel section (#9).
Screw barrel section into the front sight (near diagonal side).
Align foregrip catch with holes on front sight, tighten barrel.
Screw barrel nut (A#12) onto barrel.

Verify:
Parts are held firmly. Use Loctite to make this more permanent.

24 - install barrel
Attach barrel to receiver.

Parts:
none, use assembly from the previous step.



Work:
Screw barrel assembly (see previous step) onto barrel stub of the upper receiver.
Align front sight in correct position. Barrel will have to be partially unscrewed for this to happen - do not overtighten the barrel trying to overcome it!
"Unscrew" barrel nut against receiver to secure barrel assembly.

Verify:
This is actually a hard part. It is very easy to destroy threads on barrel due to overtightening or repetitive adjustments. At the moment I have not found the best way to do that. My barrel has lost threads almost completely - I need to use shims to hold it without wobbling. I had to adjust front sight many times, as it was just impossible to make everything work right. One of the sections always unscrewed or shifted ruining front sight alignement.
Looking back I need to make barrel sections permanently attached to each other using Loctite or maybe superglue. Only the section that attaches to receiver should maybe be left unglued to facilitate later disassembly and cleaning.
Another problem I noticed is that probably barrel does not screw in deep enough into receiver, as a result foregrip support has to be moved (by unscrewing) slightly to the front to fit into its hole in the foregrip.

25 - bolt head
Constructing the bolt.



Parts:
C#33 - firing pin
C#34 - larger spring
C#36 - pin wider at one end
C#37 - pin
C#44 - smaller spring
C#45 - extractor
#168 - bolt
C#169 - bolt head

Check:
Polish whole surface of the bolt. Get rid of casting lines and other imperfections.
Insert extractor and spring, check that a cartridge rim will fit under extractor claw! If it is too tight as on mine, you would need to add a thin (0.2mm for me) spacer to adjust extractor.



Work:
Insert spring (C#44) into bolt head (C#169), then insert extractor in its place.
Slide bolt head onto bolt (#168) and secure it in place using pin (C#37) hammered into the hole.
Check that extractor works correctly: it should slide out and go back in, NOT move outwards, and have enough clearance to grab cartridge rim when in fully retracted position.
Insert spring (C#34) into bolt, then insert firing pin (C#33) and secure it in place using pin (C#36).
Check that firing pin moves freely.

Verify:
See above.

26 - charging handle



Parts:
B#17 - tab
B#18 - plunger
B#19 - spring
B#20 - pin
#142 - charging handle

Check:
Polish all surfaces of the charging handle, except top and side of the "ears" that you will pull.
My handle had too thin slot, and neither spring, plunger or tab would enter it. I have used a long thin screwdriver inserted into the slot to slightly open it. Make sure to open whole depth, not just near edge.



Work:
Insert spring (B#19) into hole in handle, followed by plunger (B#18).
Insert tab (B#17) into the slot.
Align tab holes with handle holes, insert pin (B#20), hammer it in after placing handle on soft wood.

Verify:
Tab should pivot freely against spring pressure, without interference with handle.
Pin should not stick out of the handle

27 - install bolt
Put bolt in the receiver.

Parts:
none, use assembled bolt and charging handle from the previous steps



Work:
Insert charging handle into the upper receiver, locking tab to the left, claw to the bottom.
Insert bolt into the upper receiver, bolt head first, lug upwards.

Verify:
It is necessary to check that bolt moves relatively freely at this stage. If something blocks the bolt, or it scratches against something, you'd better find and remove the problem before you move on to the next step.

(note: photo taken at a later date, parts are now dirty from oil)

28 - put receiver together
As the title says

Parts:
none, use assembled upper and lower receiver.



Work:
Almost remove front and rear receiver pins. They should lock on their plungers in fully extended position, just short of falling out. They should clear insides of the lower receiver.
Align upper receiver with the front hole, close forward pin.
Close upper receiver on lower receiver, close rear pin.

Verify:
Make sure pins do not fall out.
Make sure upper receiver is held to the lower.
Check that bolt moves freely backwards when charging handle is pulled back. You will certainly feel not only return spring, but mainly huge friction as bolt enters dire straights between hammer and upper...
When charging handle is released, bolt should spring back to the front position. This is unlikely to happen right now, as bolt will probably get blocked by friction in its backwards position. Forward assist might help you to nudge bolt forward, eventually closing it.

Making bolt move freely is the biggest assembly challenge so far, by FAR. This is THE stumbling block for many people, as can be read on the forum

29 - foregrip

Parts:
#6 - two foregrip halves



Work:
Pull back rear foregrip latch.
Insert front end of a foregrip half (#6) onto model, from the top.
Align back end of the foregrip half onto foregrip support. It has to clear rear foregrip latch. Foregrip has slots on the inside that have to enter foregrip support. If they don't you need to unscrew support to find the right position. Foregrip half also has two protrusions that should lock between teeth of grip support. As long as grip support is fixed in place (and does not rotate) this might help to avoid foregrip wobble.
Repeat with the other foregrip half, this time from the bottom.
Release rear foregrip latch.

Verify:
Foregrip should be held between front and rear latch, and do not fall out.
Foregrip halves should be closesly together, parallel, without holes between them.
Twisting foregrip should not cause barrel to unscrew (!). If you used Loctite or superglue this is an easy one ;-)
Foregrips WILL twist slightly, as both support and forward catch have quite a bit of clearance. You can use your favourite method to secure them better.

30 - magazine



Parts:
#166 - magazine (it comes pre-assembled)

Check:
Deburr lips of the magazine. They are extremely sharp, can cut your fingers, deeply scratch cartridges, cause too much friction and prevent proper feeding.



Work:
Just insert magazine into the model. Hole for the catch should be to the left.

Verify:
Magazine should not fall out by itself.
Magazine should easily come out when mag relase button is used.
Magazine should not cause interference with the bolt.
Empty magazine should activate bolt stop. It usually doesn't, as follower plunges inside the magazine. This can be resolved by modifying the follower.
Insert empty cartridges to the magazine. Move bolt handle back and forth to check that cartridges are fed and ejected correctly.

This completes Marushin XM177E1 kit assembly.

In theory.

In practice it is still a long way to obtain a working modelgun, mainly due to bolt friction, and several other problems found along the way.

Remaining problems:

• bolt gets stuck inside receiver (no solution yet, except of plenty oil and layer of shavings that act as cushion)
  
• extractor does not grab cartridges due to too small gap from bolt head (needs bolt disassembly and installing a spacer)
  
• hammer starts destructing soon (probably due to contact with firing bar, no solution)
  
• bolt buffer gets damaged by it's stop pin (not sure if it has serious impact)
  
• barrel is not securely screwed into the receiver, it unscrews and misaligns the sight (duh...)
  
• foregrip twists and moves around (just like in real ones :-) )
  
• rear sight adjustment does not seem to work (at least I can't figure it out)
  
• stock twists and wobbles a bit (this is not a major problem)
  
• upper and lower receiver wobble due to too large clearance of the pins and lugs (should be easily fixed)
  

This model will not fire unless at least the bolt problem is resolved.

I am very satisfied by quality of parts and "niceness" of this model. It still needs some fixes for assembly quality to be a solid model, but these can be achieved fairly easily (all wobbles and barrel). Firing action still remains to be seen ;-)

One again you've posted an awesome and helpful guide!
Excellent mate!

Kiwigunner

This has got to be the best article I've ever seen ... brilliant , just brilliant

What we need next is the same Guide structure for every Marushin Kit... Keep up the excellent work smootik and thanks mate

Thanks guys :-)

It did take time and effort to put it (text/photos, as well as the model) together. Initially I though of doing a video instruction like wolfecastle did here for MP40, however it would take much more time and skill than I had.
https://mp40modelguns.forumotion.net/t2546-marushin-mp-40-instructional-video-on-assembly-in-2-parts

Posts are now updated with pictures from manual to show original instructions. These are not high quality, as you would normally use your printed manual that came with the kit, just serve as a rough guideline.

What remains now is a description of bolt assembly, and of course taking time to tune the model and make it fire.

Please, please - add your comments and hints :-) Also correct my English, especially names of parts and verbs for actions. Without corrections I will never learn how to write properly ;-)

Here's a photo of a partially blued bolt:



I used a blue felt-tip pen to blue surface of the bolt. This helped to see where ink gets scratched off bolt and is left inside the receiver - these areas need to be made smoother than smooth and inspected for other problems.

You can clearly see that the top surface of the bolt, above and to the right of blue marks, is what causes friction. Near right side you can even see two horizontal deep lines.
This side of the bolt slides against sharp edges inside receiver, where large main bolt space changes into a smaller guide space (charging handle and protrusion on top of the bolt move inside it). Bolt has a lot of play inside its channel, making damage over larger surface than just a single line.
Bolt is pressed against these edges by the hammer. Regardless of polishing and making edges round this still seems to be a problem. Only a large amount of silicone oil helps that, but even then aluminum still gets shaved off the parts - when you inspect bolt after cycling a few times oil becomes almost black. This oil/shavings mixture seems to work best as a lubricant.

Regardless of that friction problem must also be something else - sometimes after opening receiver/removing/inserting bolt it does not stick at all, sometimes it does much harder than it should.

Progress update.

Resolved problems:

• extractor does not grab cartridges due to too small gap from bolt head (needs bolt disassembly and installing a spacer)
  
• stock twists and wobbles a bit (this is not a major problem)
  
• bolt buffer gets damaged by it's stop pin (not sure if it has serious impact)
  

Problems that have a solution:

• hammer starts destructing soon (a sunk screw will be installed to resolve that)
  
• foregrip twists and moves around (partially resolved, it merely creaks now)
  
• upper and lower receiver wobble due to too large clearance of the pins and lugs (looking for right size o-ring for the rear lug)
  
• smoke seeping out of grips (silicon seal can be used on bypass cover)

Remaining problems:

• bolt gets stuck inside receiver. After more investigation it seems to happen due to receiver-stock tube alignement. When bolt sticks and stock tube is unscrewed and then tilted, bolt usually gets released)
  
• barrel is not securely screwed into the receiver, it unscrews and misaligns the sight (duh...)
  
• rear sight adjustment does not seem to work (at least I can't figure it out)
  

How hard would it be to get part x74 made up or find loose?

Its the small barrel with threads on each side that screws in to the flash hider and in to front site.

It is not so hard if you can find a fitting aluminum tube and someone who can cut a 14 mm thread into it.
A friend has done this for me in the past.
Spare parts are available from time to time in Japan, but Marushin does not always keep them in stock so it can take a while.

Thanks mate. Trying to source one as we speak. There is one on yahoo japan but i can't figure out how to buy it (don't speak japanese)

Most likely the seller won't ship abroad, so I#d recommend to ask forum member Shazhib. I think he is willing to help you. He has helped a lot of us with getting and forwarding spare parts ...

I was actually thinking along those lines. Thanks for the help!

Your best option when bidding on Yahoo Japan Auctions isd to ask forum member shazhib if he would bid on your behalf. If he's agreeable and wins the item he can ship it to you

You could also Francky (another forum member) if he's got this part in his stock.
Both members are contactable by PM here

Thanks heaps guys!

Does anyone have the dimensions for Part 78, long buffer spring? It isn't mentioned anywhere! Thank you.

smootik wrote:

13 - bolt buffer



Parts:
X#77 - bolt buffer
#78 - return spring
X#79 - small buffer spring

Check:
Bolt buffer (X#77) needs polishing of all surfaces, including the front (where bolt will hit).



Work:
Screw in small buffer spring (X#79) into the buffer (X#77). The end that is visibly sticking out goes in first, then rotate spring to the right against tension, all the way in.
Insert return spring (#78) into receiver tube.
Insert bolt buffer into receiver tube, end with small spring goes in first.
Extension should lock against plunger (D#75 installed in step 09) and NOT jump back out.

Verify:
Extension should not come out of the tube by itself.
It should be possible to freely push it inside.