Mp5 fps drop fix help

[Ammo]

Hi guys. I had a problem before with fps dropping quite a fair bit on my mp5. After asking here about it I was told, and I quote, "Most likely cause will be airseal parts, might be a case of a new O-ring on the piston head and a new hopup rubber/nub."

I originally thought it may be the spring but seems that may not be the case (even I thought it was odd that the spring would just kack up to the point that it would drop fps so much - the spring was a 1j spring).

I've decided to open up the gearbox and give the repair a go myself as I need to do this at some point anyway and may as well start now. However the advice I need is on what I need to buy. :/ Thus far on my shopping list I have the following items (all from Z1):

~ Systema Aluminium/Polycarbonate Piston Head with Bearing.
~ ICS Hop Rubber.
~ ICS Hop Bead.

Would these be the things I need for this repair? Any other recommendations by anyone? Also, I'm only assuming I need the Hop Bead - would that be the case?

Any and all help would be appreciated.

[jagillham]

Re: Mp5 fps drop fix help

I'd go for a rubber like TM, Guarder clear or Systema.

Piston head choice is fine. I'd rather a plastic one (weak V2 gearbox front end to consider).

But bearings and vents are a must!

Edit:

My choice:

- Systema Polycarbonate Piston Head with Bearing
- Systema Hop Rubber

Only other things worth considering for air seal would be the cylinder head and nozzle.

[ThatblokewiththeScar.]

Re: Mp5 fps drop fix help

Pretty much as above. I would definitely say go with a standard TM hop rubber and if you want to change the Nub get a H-nub. No need to spend out on the systema almost any vented bearing head will do. I would personally never put an aluminum piston head in any gun least of all a V2. While you have it open if it does not already have bearings or metal bushings now is the time to pop some in. And don't over do the grease Less is More. :D

[Ammo]

Re: Mp5 fps drop fix help

So this is what I have on my shopping list...

- Systema Polycarbonate Piston Head with Bearing
- Systema Hop Rubber
- Systema Version 2 Cylinder head
- Systema Air Seal Nozzle (MP5A4, MP5A5, MP5SD5 & MP5SD6)

Does that sound good? I've heard that the systema stuff is supposed to be really good as well so hopefully this will fix up the air loss.

[jagillham]

Re: Mp5 fps drop fix help

It can't hurt :D

Depends what you feeling like doing, you probably could identify the offending part in the weapon and only replace that. Or you may prefer to do everything in one go.

[Ammo]

Re: Mp5 fps drop fix help

I wouldn't have a clue how to identify the problem - have never opened a gearbox before. At the moment I may end up not keeping the MP5 anyway (thus far its on sale). I was thinking about getting a CA SCAR-H. If not though then I will just fix up the MP5 and if it means opening up the gearbox may as well replace everything worth replacing so I wouldn't have to open it all up again and I can get some decent fps for my next game.

[ThatblokewiththeScar.]

Re: Mp5 fps drop fix help

If you have the patience do each upgrade/replacement one by one. Don't forget you are trying to solve a problem first not just pop in some upgrades.

So start with the easy bit and change out the hop if that's OK move inside the gun. Changing the nozzle then the cylinder head and then the piston head. Believe me I know it sounds like a lot of faffing around but it's even worse when you change everything and it has still not solved the problem or it's caused a few more. Thats when you see people selling gearbox's as "for spares or repair"

No one said it would be easy but remember it's also supposed to be fun.:D:D:D

And yes the systema stuff is very good quality.

[Ammo]

Re: Mp5 fps drop fix help

It'll certainly be a fun project for me to undertake as I been wanting to learn more about the internal workings of AEG's. That sounds like a smart plan too. I'll start from the basics and just try one part at a time until I see that the problem has been fixed. After looking at a load of youtube vids on how to take a gearbox apart I think I'm ready to give it a go. :D

[Could Not Think Of A Name]

Re: Mp5 fps drop fix help

It\'ll certainly be a fun project for me to undertake as I been wanting to learn more about the internal workings of AEG\'s. That sounds like a smart plan too. I\'ll start from the basics and just try one part at a time until I see that the problem has been fixed. After looking at a load of youtube vids on how to take a gearbox apart I think I\'m ready to give it a go. :D

Walks over to MP5, takes out gearbox. DROP, smash. LOL
Just kidding mate, good luck with your 1st try.

[Ammo]

Re: Mp5 fps drop fix help

Thanks, lol. :P I'll probably post an update once I get started on it and see how it goes. I have to find out first though if I want to keep the MP5 or sell it and just buy the SCAR. :/ Am still half and half on selling it, lol.

[Ammo]

Re: Mp5 fps drop fix help

Just thought I would update on this... I've ordered all the stuff I need to upgrade/fix this up hopefully and plan to take apart the gearbox and start implementing all the new parts into it on Sunday. I don't have access to a chrono so I may just have to upgrade all the parts unless the problem is visible to inspection of the parts in question. In which case I will replace only what needs replacing and return the unused items back to Z1. I figured ordering all in one go would be better so as to avoid multiple P&P charges, lol.

[Ammo]

Re: Mp5 fps drop fix help

I know it's been a long while but I thought I would update on this (finally). I had at one point decided not to take it apart but then eventually curiosity got the better of me and I did. As well as the parts I listed I also put in a new M100 spring - just to add that little more power to the gun and brought a new 6.03 TB barrel for it too.

The barrel change was a simple matter - even the hop unit was easy to work with. The gearbox, as intimidating as it may seem for someone whose opening it up for the first time went very smoothly actually. Followed everything I had read up about it and used a video on a certain web site as a reference which incidently helped a LOT when it came to explaining what all the parts in the box do and how they function properly.

The first time round (after putting all the parts in) the gun didn't work properly and after a shot or two just stalled so took it all apart again and back together again this time paying more attention to all the gears being in there properly and securely and after that worked perfectly. A very nice 330-335fps (without the precision barrel cause after that it just ran too hot for my site). Working perfectly fine now so thank you everyone who gave me advice on this.

[jagillham]

Re: Mp5 fps drop fix help

Well done

Always good to see somebody willing to give it a crack rather than run to a shop techie at the first sign of trouble!