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The Quest for a better TM MP7A1...


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I'm sure you've seen FarEast's excellent review which discusses the gun in general and gunner-airsoft's stripping guide which shows how to tear into the gearbox and get the hop up unit apart. I'm not looking to duplicate any of that information at this point but it's going to happen in the process of reaching my ultimate objective.


My goal today is POWER. Not the absolute kind, I understand that corrupts to some degree so I'm taking a pass there. It's not muzzle velocity I'm after either, though that it the long-terms goal which makes this investigation necessary. No, today I'm after electrical power. Simply put, this gun needs more!


I'm loving my MP7, don't get me wrong. It's a fun gun. But, it could use better trigger response and a higher rate of fire. Longer more consistent battery life would be nice too. The best way to get all this currently is to increase the voltage and switch to NiMh cells. To do this I must find room for at least one more cell in this already tight package. If I can fit even one more cell, the gun would be improved immensely in my opinion. And, it would provide the power needed to run an upgraded spring should one become available.


Feel free to skip down a bit if some of this is old news. As usual this will be multiple posts due to the ten pic per post limit. Lets get started.


We're going to turn this...



...into this. Note that it's not necessary to remove the flash hider and side rails for this, mine were simply removed already. You'll need to remove the sights if they're in the way of the top rail screws.



Start by removing the stock. Pull both catches up and slide the stock out and free. Take the front set off too



Next take the top rail off. The screw above the selector is a dummy, don't remove it. The longest screw goes in front, keep this in mind when you reinstall the rail later.



Pop the charging handle return spring off using a small tool and set it aside..



Remove the charging handle retaining screw next. You may also remove the charging handle at this time.



Now remove the body pin screws.



And then push out the body pins.



The end cap will be free now. Remove it and set it aside.



Here's the inside view at this point. You can see the back of the gearboix.


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The next step is to remove the serial number plate. It just slides out.



You may then remove the gearbox retainer shim. The gearbox will slip down a bit after this is removed.



Look above the gearbox and note the semi-auto cutoff lever actuator arm and it's connection to the semi-auto cutoff lever. You'll need to get this back correctly when reassembling the gun or you will not be able to switch to auto.



Now pull the gearbox out of the back. You'll need to disconnect the wires first of course, they need to be fed through the slot in the top as you remove the gearbox.



When putting the gearbox back in you'll need to use a small tool to pull the wires back up.



Here's the gearbox. It really is very small.



The inner barrel assembly can now be removed. It'll just slide out.



Here's the hop up unit as viewed from the left side...



...and the bottom...



...and the right...


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...and the top....



...and the back.



Now is a good time to remove the 'bolt'. Slide it back as far as you can.



Press down on the part towards the top.



Here's another view. Pressing this down will allow it to come free of the track inside.



It can then be pulled out the back.



Here are all the rear set components.



Now it's time to take out the selector lever, trigger, and bolt release so the switch assembly can be removed. Start by pushing out the bolt catch spring pin. Don't lose it! Pull the lever off and set is aside as well.



Now pull out the lever very carefully, pay attention to the spring's position.



You can see the hooked part catches the post in the lever and the straight part fits into a notch in the hole.


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Now push out the trigger pin. Don't force it, it's designed to go one way. If it feels tough try pushing from the other side. You can see in this pic the side that should come out first has grooves in it.



With the pin removed the trigger is free. I was worried that the trigger would be a nightmare to get in and out but it's fairly easy.



Just pull it forward and out. Pay attention to the spring as you do this so you have an idea how to get it back. It's basically the reverse of removing it.



Next knock out the selector lever spring pin and remove the selector lever. Set it aside in a safe place along with the lever parts.



Here's the left side of the body with the bolt release, trigger, and selector components removed.



And here's the right side.



These are all the components that were just removed.



Looking in the back, the switch assembly can be seen. Carefully remove it from the gun using tools to poke at it from the front if need be. It's held in position by rails and can be tricky to get back in place. Just take your time and poke at it through available holes. You'll get it.



Here's the right side of the switch assembly.



And the left.


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Another look. you can see the battery connector in the front.



The fuse is rated at 10A if you were curious. The gearbox must not be very demanding.



Here you can see where the barrel goes though the assembly.



Here are all the major internal components.



Here the are as they would be inside the gun when assembled as viewed from the left side...



...and the right.



This is the connection between the semi-auto cutoff lever actuator arm and the actual semi-auto cutoff lever that was mentioned earlier.



Close up on the left side of the switch assembly.



And the here's the right side.



This is the bottom, you can see some of the trigger mechanism.


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Here you can see some more of the trigger mechanism.



This is what the selector mechanism looks like on safe.



This is semi. It's a small difference.



On auto the selector plate pushes against the cutoff lever actuator arm which disengages the cutoff lever in the gearbox.



Here's a look deep inside the gutted body. There are still a few bits in there but there's no need to remove them.



And now more shallow look.



A view from the front.



Based on my observations, I've come up with this concept for a custom made, permanently installed 8.4v 750mAh NiMh battery.



Basically an extra cell would be located in the auxiliary space above the hop up unit while the rest of the battery would be located in the normal space. I've taken some basic measurements and I believe that an additional 2/3AA cell can fit here. The battery would be charged while still in the gun via a pair of leads with slide connectors that could be accessed when the front set is removed.


It would be built with CBP750 2/3AA NiMh cells, unless better cells become available. I expect this battery would offer about the same or perhaps slightly less runtime at near-peak performance as two normal 500mAh packs thanks to the superior discharge characteristics of NiMh cells. You can see by the graph that at 10A these cells go to almost 650mAh before dropping below 1v. This is much better than TM's NiCad solution which probably drops off significantly after 300mAh (a conservative estimate). Certainly it would afford enough power for part of a day's use as a in a primary role. As long as a fast charger is available to charge the battery between missions the gun could be used all day with no need to change the battery mid-game (helpful since you couldn't change it in this configuration).


The extra 1.2v would increase trigger response and ROF to a more satisfying level and allow for limited upgrades, perhaps to 300-328 FPS (though getting the parts to do that is a separate issue).


I will be taking a more in-depth look at this concept in the future. I will draw up an exact configuration in the form of a wiring diagram with lead lengths included at that time. I will then submit it to CBP for them to build. Once I have it installed (assuming it is in fact possible) I'll update with results. I'm looking forward to it as it means that upgrading the MP7 to a reasonable power level will be possible without using an external power source, should the necessary upgrade parts become available in the future (namely a stronger spring and metal bushings).


Larger versions of all these pictures and more available here. I am working on a comprehensive review which will be available in the future.


More to come...

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Cool idea. I've never seen an MP7, so this may be a foolish idea, but would it be possible to add a remote cell to the foregrip? This would require drilling and most likely dremeling, but maybe is worth looking at if your idea doesn't work. I want an MP7.

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That was my original thinking as well. However I took the foregrip off and there's really no room in there because of the retention mechanism. If you sacrificed that part (in other words if you made the grip fixed in either position) it could probably be done. However, it's less than ideal.

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Great idea, especially since I've heen hearing about power being an issue from some MP7 owners.  I actually want to buy an MP7 just to disassemble it following this very guide. 

Good idea. And when you're done the MP7 is fun for other things besides violating it too. :)


Make one for the TM G36c, and I'll tear mine apart :)

A guide you mean? In fact a comprehensive G36 guide is one of my current projects...


How much would CBP charge for such a battery configuration with those type of cells?

It should be around $14 plus shipping.

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Great internal breakdown. I hope you can get the power up to 300+.


One thing to note, how would you charge the remote cell? I take it that the gearbox would have to be removed, or the top rail field stripped, in order to replace the remote cell in combat. Might be a bit of hassle.

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As I said, you would not remove the battery to charge it. It can not be easily changed. Instead there would be leads wired in up to the front with slide connectors so you can charge it directly while still in the gun. For this to be a viable all-day gun in this configuration you would need access to a fast charger most likely. This is not a problem for me as I usually top my guns off at lunch using my fast charger which I can hook up to my car. However depending on your play style it's possible the nearly 650mAh of usable capacity may last you all day.


It may be possible to implement it in such a way as to allow the main set of cells to be removed and the auxiliary cell to be disabled so that the standard battery could still be used in a pinch. This will require a more in-depth look going forward but I'll see what I can do.

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You know i was just wondering, why are you 750mah AA cells when you can use 1650mah AA or 2300mah AA that is shown on the CBP site? forgive me if i sound stupid it's abit late over here and i ain't thinking properly, but logically assuming the higher the MAH the battery produce, doesn't it mean we can put in the same or less cells as the original, thus eliminating the need to put in the extra cells in the space you found?

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No. There is no space for six or more full AA cells. We can't use less than six cells either, we need six cells to get 7.2v at least. Capacity is no substitute for voltage.


1.2v per cell (in series) x 6 cells = 7.2v. :)


1.2v x 7 = 8.4v. :D


1.2v x 4 = 4.8v :(




Also, we could build a simple 7.2v replacement pack with the CPB750 cells of course, but we'd need the custom connector for it. Anyway the point of this exercise is to get more voltage.

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No no, Pay attention! You can't fit six AA cells. :waggle: You need 2/3AA cells. Full length AA cells will not fit! CBP750 cells are 2/3AA and they are your best choice.


Furthermore those 2300mAh cells they have there are not intended for motor use. Their discharge rate will not suit our amperage demands.

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Ah just re-read your post, sorry. :(


but..can't i fit in four 2300Mah AA cells, and make it up with say...two more 750Mah 2/3 AA cells to make up the differents?


or mixing different Mah rating is a no-no?

Correct. Mixing mAh is a no-no. And it still wouldn't fit. Or work.

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Yes, generally I too find when I start thinking 2 and 2/3 = 2 I'd best be off to bed. :D


You could still build a six CBP750 cell direct replacement at the expense of your stock battery. It would be as good as about two standard 500mAh packs in terms of usable capacity. It won't solve the need-for-voltage issue though.

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You could go ahead and build a 6 cell CBP750 pack, and then wire in a mosfet, capacitor bank, or both into the little space above the hopup. That won't help too much with power upgrades, but trigger lag will go down adn ROF will go up. I think your extra cell plan is probably the best bet, but if it doesn't actually fit, or you find you really want a removable pack, mosfet switching and capcitors may provide some of the opwerformance attibutes you're looking for.

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static, a quick question if you don't mind.


If you remove the front RIS rails, above the foregrip (if folded down, deployed) there is an oval hole with a circular hole in the middle, which looks like it's running through a metal block. The screws off the RIS rails don't fit in the hole - it's marginally too wide so they just drop in and don't thread.


What is the hole, and what purpose does it serve?

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