Ciphers TM Mp7 From Hell

[Cipher-032]

EDIT: This thread is dedicated to my very old, abused, probably 4th hand TM MP7 GBBR. You’ll find some good sources of fixes below.
 

 

A month or so ago I bought a slightly used, and abused second hand TM MP7 GBB with 5 mags for a decent price. Came with a few extra's. Which is great!

Needless to say this gun has been a labour of love to get working right. Leaking mags, broken parts of the chassis. Much swearing and threatening to throw it off a cliff. But I kept at it.

So, After every thing is finalised. It has a Mod Tan bucking, and the Nineball gas routes fitted. It also came with a Guns Modify nozzle. Fill a mag with green gas (Nuprol 2.0) and im getting 360FPS. Pop a stock gas route back in and it starts creeping to 370. I had the thing firing at 380FPS at one point!

So I buy some Nuprol 1.0, and it fires bang on 350. Only downside is I had to trim a coil off the buffer spring (The spring on the stock plate) for the bolt to travel back far enough to engage bolt lock reliably. 

So if I find and fit a stock nozzle, and return it back to stock it might fire 350 on Nuprol 2. What FPS readings are you getting?

It be nice to run the gun safely on Nuprol 2 for the crisper function. But I have no idea if the FG discs will fit, and no known NPAS's are available. (That I can find). I have no clue why this thing fires so hot! (For a TM any way)

I will mention, I did use it on a warm afternoon, on Nuprol 1, with the little tweaks, and it worked well! But god the recoil spring is sill weak to reset the auto sear. Hate having dead trigger after bolt release!

[Wo1f]

When I got mine (also used and abused) it was bog standard and firing 348 on propane. It was very consistent but far too close to the limit for my liking on a GBBR. 

 

The gas routers are probably upping the FPS as well as the nozzle. I’d try to stick to standard where possible. 

 

I wouldn’t have cut the recoil spring. You can mod the arm to make the lock more reliable. 

 

Theres also a mod to fix the dead trigger where the bolt doesn’t come forward enough to engage. 

[Davegolf]

There is a wealth of knowledge on YouTube on these issues, I can't remember the guys name / channel but I'm sure @Wo1f will

 

Leave spring standard.

[Cipher-032]

Found the guy, he’s called Rouge some thing. He explains the issue well, says to make the sear spring “lighter”. 

 

Ive trimmed the said spring. And makes little difference. The issue is the bolt not hitting home with enough force to hit the sear. He also said that a 150% recoil spring will help the issue. So I’ve found a creation recoil spring and ordered it from China.

 

ive also polished the chassis and bolt for extra cyclic rate.

 

@Wo1f, the nineball routes help keep the FPS down a touch but offer good efficiency still. Once I can nab a stock nozzle I will. Just hope they can stand Nuprol 1. If not I have spares!

[heroshark]

Has it got a different non stock shut off/rocket valve in the nozzle? Looking into it there's 2 versions both come with the stopper/rocket. One is high flow and a 1J one  https://www.airsoftzone.co.uk/reinforced-nozzle-ver-2-japan-1j-for-marui-mp7-gbb-guns-modify.html

[Wo1f]

Fix for the dead trigger:

 

Either tape the car or add a bit of material to the trigger. Either half a mm of epoxy or cut some thin plastic/paper and glue it. 

[Cipher-032]

@Wo1f, the bolt is failing to engage the full auto sear, which causes the dead trigger. I might try what you’ve suggested. Either that or I’m adding some rod to the bolt to contact it sooner

 

@heroshark, I have the one you linked fitted to the gun. Granted it fires at about 1.1j on a 2 with Nuprol 1

 

also the rocket valve decided to go boom in good fashion today! So the MP7 didnt get used. A lot of carnage in the barrel. 

[Cipher-032]

So I made a break though with the MP7 today.

Parts came from Eagle 6. New rocket valve and the dodad that holds it in. The OEM Rocket valve is much smaller and has a restricter in place. FPS is now 310 on White, and 330 on green! WHOOOO!

We are finally making steps! Now to swap gas routers and see which provide a better seal. Most likely TM.

My 150% recoil spring is now dispatched from china, which will solve the dead trigger for sure.

Also renamed the thread for something more fitting.

Keep tuned for more things to go wrong. Im sure they will!
 

[jcheeseright]

150% recoil spring may be a bit much,it'll sap your gas usage loads. 

 

I used to use a 120% and that was fine. 

[Cipher-032]

22 hours ago, jcheeseright said:

150% recoil spring may be a bit much,it'll sap your gas usage loads. 

 

I used to use a 120% and that was fine. 

Cant really find parts for it any where to be frank. Only one I found was the 150% spring. So its that, or modify the sear. Which im considering doing. 

I always have a tin of gas with me on the field so if I run out, its not an issue.

[Wo1f]

Did you not try the trigger mod?

[Cipher-032]

25 minutes ago, Wo1f said:

Did you not try the trigger mod?

I did, and as I assumed, its the bolt not contacting the full auto sear. You can add all the tape you want to the trigger bar. Its the bolt that has to contact that sear, to release the hammer. The trigger bar doesnt effect it. The best way to simulate this is by removing the chassis from the body.
Remove the trigger bar and spring
Pull down the hammer by hand.
Then pull the semi sear (The part the trigger bar connects to) all the way forward. I guarantee nothing happens. 
Reach in and push the Auto sear forward, and the hammer will now fall once you pull the semi sear.
Unless the newer sears are modified slightly, and my MP7 has a very worn out sear/older design. The only fix is to add material to the auto sear, the bolt, or use a stronger recoil spring

[Cipher-032]

I already bought a right hand chassis because of this issue, but now the left hand has broken... urghhhhhh! That’s another £30 odd part I need once in stock 

[Cipher-032]

Okay, so actual progress now!

 

i did my sear mod. 2mm drill bit, extra due care, some glue and 2mm rod.

 

Rack the gun, she shoots,

 

bolt locked back? New mag in and send it home, she shoots.

 

Much more reliable now! Hopefully she stays that way so I can use it for a game!

 

[Wo1f]

To stop the cases cracking at the pin point buy the rear sling mount. The metal bracket secures the pin to it and eases pressure off the frame. I’ve got one fitted after breaking mine and it’s been great since. 

[Cipher-032]

19 hours ago, Wo1f said:

To stop the cases cracking at the pin point buy the rear sling mount. The metal bracket secures the pin to it and eases pressure off the frame. I’ve got one fitted after breaking mine and it’s been great since. 

Im guessing thats how some one singed it in the past. It came with a magpul style RIS sling point with the gun.

[Cipher-032]

So after a iffy afternoon, the MP7 held up, and didn’t break. Running stock recoil spring and white gas she fired 330FPS on sight chrono with Nuprol 1.0.  shot true and far, and got many kills. Mags become lack luster towards the end. So going to swap gas routes back round and see if that helps. But it’s likely the gas.

 

i love how small the gun is and how easy it is to run with it. Brilliant!

 

[Cipher-032]

Been a while since I’ve added here. This thing still giving me jip!

 

Rear slung mounted added. Part of the back plate replaced after a little bridge over the stock broke.

 

Ive modified the bolt slightly, grinding material away with a deremel to increase bolt lock reliability.

 

All mags are now have been serviced. New base plates O rings fitted thanks to Eagle 6, plus a smear of RTV. I put WAY too much in some last time.

[Tiercel]

Holy necrobump batman.

 

How did this gun get on for you in the long run? If you still have it, or however long you had it especially after fitting the 150% recoil spring. Similarly Id like a 120/130% one perhaps to minimise stress on the gun, but they dont seem to exist, seems to be 150% or nothing.

 

Asking because my MP7 has developed the dead trigger for apparently no damn reason. Was working fine, put it away after a game and a year later when its actually warm enough to run a GBB again, it has a dead trigger, ugh.

 

I've tried trimming the sear spring and sanding/polishing the secondary sear as per the Rogue video and its working about 80% of the time but thats obviously not good enough. Next step Im thinking is to fit a 150% spring as that seems to have solved your issue? Annoyingly most of the guides to fixing this are several years old and full of now dead imagine hosting accounts or have since been deleted so half the guide is missing.