My M16 arrived last week. I started to build it and in less than 3 hours, the job was done.

Only there is a big problem with the bolt. At first, it didn't seem to 'fit' in the receiver.
Actually, the receiver was the problem, because the bolt from the M635 (also marushin, so completely the same) that I have bought from Kickback also gave the same problem.

When I just had the upper half of the gun in my hands, so just the receiver, I could slide the bolt in the receiver, but about 5mm before the end, it just stopped. I had to push it really hard forward to get it in 'closed' position.
In the meanwhile I kinda fixed this problem by sanding the complete inside of the receiver.
So when I'm just having the receiver in my hands, the bolt goes smoothly in there now.

But then, when the receiver is fixed on the lower half, and I pull the charging lever, the bolt moves backwards, but it does absolutely not go smooth! No problem in the first 2 to 3 cm, but then I have to pull the charging lever quite hard to get the bolt where it needs to be, and when it finally is there, it doesn't move forward anymore (no it is not the empty magazine catch ). I have to use a screwdriver to move it back forwards. Sometimes even that doesn't work and then I really have to take off the stock and the tube to remove the bolt that way, because I can't 'open' the gun the normal way, cause the bolt is half in the gun, half in the stock.

What can I do???? Please help me guys!!

1. Is there any excess material on the top of the T charging handle that is perhaps forcing the bolt down too far when the upper and lower receiver is closed ?

I know the quality control in the kits does seems to be getting worse but this does sound poor.

2. Are you sure the hammer is free to move out of the way of the bolt ....the spring is in correctly ?

3. also make sure the forward assit button moves freely and is not partly stuck in because of excess material on part # 27 ( the fixing pin for this assembly can hold part # 27 too tightly )

Let us know what you find

DOC

p.s I`d look at point 3 first

Hi Yellow,

Doc has made some really good points there mate so i would start with them,but... the m635 that you purchased from me worked great when it left me and the bolt had no problems ,so its obviously something that has happened since ,i would also have a look at the pin on top of the bolt that holds the firing bar in place,as this sometimes works itself loose and grinds on the upper reciever groove just below the charging handle slot (hope that makes sense!).
Other than the options that Doc gave you its also worth checking that the ejector is screwed in correctly,and is parallel with the reciever as this can scrap on the bolt too.
I'm sure you will sort it out mate

Kickback

Don't worry Kickback, think you misunderstood
I just tried to place the bolt from the M635 into the M16 and that gave the same problem, so the bolt itself couldn't be the problem. I didn't have the chance to fire the M635 yet, but it runs very smoothly!!

I will try to check the other points later this evening or tomorrow and I will let you guys know, but as far as I know, the hammer works correctly and I think the forward assist works good too.
The bolt seems to get stuck after the first 2 or 3 cm. I also tried to slide the bolt in the tube in the stock and that also goes very smooth. Strange case

Hi yellow,

Does the M635 bolt assy slide smoothly in your M16

This might prove useful too, even if it is written in Japanese

Hi Cerwyn

No, with the M635 bolt it's still the same problem, so it must be the receiver of the M16.

When I only have the upper receiver in my hands, there is no problem anymore. Then the bolt moves as it should.
But when the upper and lower receiver are assembled, I can pull the charging handle (and the bolt) 35mm backwards without any problem, but then it all starts. From that point the bolt really gets sticked.

- I've checked the forward assist, but this can not be the problem.
- I've also spent another hour of sanding and polishing the receiver and the bolt, so that can't be the problem anymore either.
- The charging handle is clean on top.
- The hammer moves as it should and I think the springs are in correctly.
- The pin on top of the bolt for the firing bar is fixed tightly.
- The ejector seems to touch the bolt sometimes a little bit, but not enough to cause the problem. I've tried to bend it a little bit, but I haven't found the right position yet. Have to try some more later this evening.

Any other points I should look at?

Spent another hour of sanding the upper receiver, bended the ejector a bit in a few positions and put some oil on the bolt.
I couldn't believe my eyes, but the bolt moved forward again!! So happy me
It is not going as smooth as my M635, but it gets no longer sticked. Maybe it will work better after some 'use'.

But here are the next problems:
- with the 20 rd magazine within the kit, I can't get a round in the chamber. I already sanded the lips of the magazine, but without any succes. It seems that the bolt doesn't have enough force to get a round out of the mag.
Then I tried the 30rd magazine that I got with my M635, and there seems to be no problem, so the problem can only be the 20 rd mag. Any other tips besides sanding the feeding lips?
- then, when I get a round chambered, and I pull the charging handle again, normally, the extractor must extract the round from the chamber, right? Well of course, it doens't...
Any tips and tricks?

Hello yellow,

Well at least you're getting closer to a working model with every step

If the 20rd magazine is causing problems, check that the feed lips are at the same angle and profile as the 30rd mag you have. The position and angle the cartridge sits in the mag makes a big difference.

You mention that you've had to bend the extractor a little to get the bolt to travel fully. If chambered rounds aren't being pulled out, it's very likely the extractor claw isn't gripping the cartridge rim.

To check this, load the mag' with a round and chamber it.
Slowly pull the charging handle back, keeping a close watch on the ejection port. If all's well, you should see the cartridge being pulled out of the chamber. The slower you do this, the easier it is too see what's happening.
If the cartridge remains in the chamber, either the extractor claw is set too high, failing to grip the rim, or possibly too low so it cannot slip over the rim to grip it.

Next test is take the bolt assembly out of the reciever and place a cartridge into the bolt face. The extractor claw should hold the cartridge in place by it's rim.
If it doesn't, you may have bent it too far.

There's also a slim chance the cartridge is jamming in the chamber. Make sure the detonator pin is tight in the chamber.
Load your cartridges up with used "dead" caps, greasing them as you would normally. There's less chance then of the cartridge internals tipping over inside and jamming up.

Hi Cerwyn

Thanks for your tips, and indeed I'm getting closer to get a working model, but I hope that time will come soon

I can't really compare the 20 and 30rd mags, because I think the 30rd mag is not a Marushin. It has some kind of gold finish and the cart follower is completely different (black plastic instead of grey zinc). Anyway, I will try to bend the feeding lips a bit. Maybe it helps.

I had to bend the ejector a bit for the bolt to move smoothly, but I didn't bend the extractor.
So the ejector can not be the problem yet, because the carts don't get that far yet, but I guess that will be the next problem

I already tried what you say: placing a cart in the mag, chamber it, and pull the charging handle slowly backwards, but the cart doesn't get catched by the extractor.
I also tried to place a cart in the bolt face, and there is no problem, the claw holds the cart.
You mentioned that the extractor claw could be set too tight, but where/how can I adjust that?
I didn't think about it yesterday, but I could also try the M635 bolt again.
I did not load the carts with a cap. I tried it with an completely empty cart, so also without the internal brass ring. But could that be the problem?? I thought I would have the biggest chance on succes with an empty cart. I will to put a cap in this evening. Is 1 7mm cap enough? Or do I have to use 2 in reverse ways?

I'll keep you guys posted

Hi yellow,

Please forgive me yellow, I had not read your post carefully enough and concentrated my thoughts on the extractor.

The extractor is spring loaded (I think it's shown as part no. 44 in section 25 of the instruction manual). Could be worth double checking that the spring is located properly or even bent/broken.

I would have thought that empty cartridges should cycle ok but just possibly a truer picture of what's going on would be seen if you loaded the cartridge with it's washer and a single dead 7mm cap.
You mentioned loading with a 5mm cap reversed... I understood that both live caps face the same way, the 5mm sat inside the 7, charge facing the cartridge pin. If you reversed the 5mm cap, the pin would strike the plastic base and fail to fire.

Are you loading them as shown in http://mp40modelguns.forumotion.net/marushin-m16-xm177-series-modelguns-f20/loading-marushin-556mm-m16-xm177-cartridges-t1252.htm

I don't have a 635 model so can't comment on the magazine supplied with it. Marushin 30rd mags are available, although very rare these days. I have one in a grey finish, not blued as the standard 20rd mag.
The Gold finish is something I've not seen before, hopefully the M16 series experts here can help.
I know that real M16 series magazines will fit the Marushin models with some modification to the catch hole but he real mags' feed lips need serious work to make them work in the modelgun.
As yours fits and feeds fine, I'd suggest it is quite likely a Marushin mag. Members like Kickback, Doc, MadMike to name just 3 could probably confirm that or correct my assumptions

No problem Cerwyn! I'm very happy that I can get all this help here!

You are talking about a 7 and a 5mm cap, but I thought I read something about 2 7mm caps.
1 used cap as a gas seal (reversed) and 1 new cap the normal way, but now I don't know it for sure anymore.

I bought my M635 from Kickback. He made a Marushin XM177 to fire 9mm rounds himself, and he also sent me the 30rd mag with it in case I wanted to convert it to 5.56 again

Hi Yellow

Loading Marushin 5.56 rds has been the core of many debates as to which is the best method.

You're right, one method does use one "live" 7mm cap, with a "dead" used cap placed , reversed, over the firing pin. This dead cap acts acts as a gas seal.

Second method, and one recommended by Marushin, is to use 1 x 7mm and 1 x 5mm cap as shown in the loading guide I linked you to.
Now, there is a strong argument saying that if the modelgun's set up correctly, then one 7mm cap should be enough. The argument was backed up by saying that Marushin sell caps too... one way to sell twice as many caps
Marushin recommended 2 live caps to ensure enough power's produced to cycle the metal bolt.

Double capping isn't always a good idea. Marushin cartridges, especially the 9mm MP40/UZI type can blow the cartridge base off if 2 live caps (7mm & 5mm) are used. The threads cannot take the pressure.
I've tried using 2 caps in my Marushin MP40 and had nothing but jamming problems as the blowback was far too strong for the bolt and recoil spring to cope with.

It would be well worth your while trying each method once the model's firing. If you can get it set up really well, one live cap with a reversed dead cap as a seal might well be plenty.
On the other hand, you may find 1 x 7mm & 1 x 5mm is needed

For testing, and "dry firing" as you are, you won't need the second dead cap inserting into the cartridge, just the one dead cap acting as the live one is fine.

Pffffff, just tried the bolt from the M635 in the M16 and that bolt DOES extract the carts.
So the new bolt from my M16 kit doesn't do its job, and I just can't see why, so I'm still having a big problem...

I've also modified the 20rd mag a bit.
I sanded the feeding lips a little more, and I filed a little bit on the front of the mag (where the rounds leave the mag).
I found that the rounds sometimes hit that place and got sticked in the mag. Seemed like the front of the mag is just coming to high to let the carts leave the mag.
I also noticed that the back of the carts (the rim) sometimes doesn't touch the feeding lips, so the carts sometimes are in a slightly different angle than they should be, allowing the bolt to slide over the carts, instead of catching one.
I don't know if my explination is understandable or not without pictures, but I try my best.

I'm actually starting to dislike this gun and if I were Marushin, I would be ashamed to sell such low quality stuff.