agm mp40 gearbox upgrade

Strip the box, clean everyting, it will be full of lithium grease, clean it all off, including the piston / cylinder, re assemble fitting the following new parts, metal spring guide with bearings, a new piston & piston head, I recomend the TM standard type piston & a systema area 1000 piston head ( without bearings, its cheaper & lighter ) systema oiless bushings, you will have to re shim the box too, re assemble & re grease using lithium grease sparingly on the gears / bushings, on the piston use silicone grease, I recoment marui silicone grease or systema silicone grease as the UK avalable grease Servisol & Abbey are too thick & cost you FPS, for a main spring go for a PDI 150% spring,

Steve.D

many thanks steve, just what i was after.
cheers
jay

Hello,

Did any of you try to replace the nozzle? I think this is the "weakest" part in the gearbox. I experimented with replacing
many other parts like, spring and piston but did not get a significant improvement in performance.
Which nozzle will fit?

Thanks!

Hi, little hijack here I'm also going to do a lot of gearbox improvements, so if anyone knows which nozzle will fit... You'll be helping me out too! Thx ^^

hi all
got my sten firing today and it feeds flawlessly but it needs a bit more of a punch. the agm mp40 gearbox inside it shoots at 280-300fps but i would like to take it up to 350fps. i know a couple of guys on here have upgraded their mp40's so was wondering if one of you guys could tell me the best way to get it there.
any help much appreciated.
jay

Just a note to say that 350fps will put you over most sites 330pfs limit for an AEG.

280 - 300 fps is perfectly fine...

Instead of trying to up your fps, make sure that your hop-up is working well. You'll get much more improvement in accuracy and range from that than from increasing the fps.

Take this from someone experienced... I've had guns down at 230fps happily engage targets at long range because the hop-up was set up correctly. I've also spent many months on other guns taking the fps up to 340fps ranges and still be totally let down by the hop (that was in my early, inexperienced days).

For the sake of the guy you're shooting at, just work on the hop unit and don't think that fps is the "be all and end all" of upgrades...

After that work on upgrading your fieldcraft and learn to hold fire until you can see the white's of their eyes.

Yith, i completely agree with what you wrote!

Still i would like to exchange the nozzle, it easy to do and should give much better performance. At least on my MP40
this must be the part that causes some problems (already tried to exchange most of the other parts).
I can not find a nozzle that fits. So if anybody knows which one will fit, please let me know

There is no off the shelf nozzle that will fit, the newer MP40s seem to have a better one than older ones, I made a custom one by cutting one down, I can't remember what it was off though, AK ones are way too short, a modelers lathe would be usefull as I use a file & an electric drill, I think if a AK hop unit was used you could then use a AK nozzle,

Steve.D

... learn to hold fire until you can see the white's of their eyes.

Bit of cold steel, sah, that's what you want ...they don't like it up 'em you see, sah, they don't like it up 'em !!!

Sorry, couldn't resist

Have been following the thread with interest as I'll be using my AGM MP40 for the first time 'in anger' come the end of the month ........ do I get the impression then that's it's not worth the hassle of opening it up at all ??

... learn to hold fire until you can see the red's of their eyes.

Husky - Sunday morning....

Agreeing with Yith. To quote Sgt. Heide talking about his new MG42 at Husky: "I want good range, I don't want stopping power".

i see what you are saying guys and would not touch my mp40 as to me it fires fine. but on my sten when you make your own design of hop unit it is very difficult to get a perfect air seal, it only has to be slightly out on one of the dimensions to make fps drop off. in making the gearbox put out 350fps the true fps would probably be about 310. otherwise it means reproducing a new hop unit which was a pain in the ass, as it would be even more of a pain to rectify the old one.
hope this makes sense.
cheers
jay

hey,
i had my agm mp40 upgraded by fire support and what a amazing job they did. well the parts they fitted are as follows -

- v3 bearing spring guide
- tm piston and piston head (standard)
- area 1000 cyclinder
- area 1000 cyclinder head
- area 1000 metal bushes
- tm ak hop unit
- tm mp5 inner barrel
- guarder sp90 spring
- guarder improved hop rubber

they kept the original nozzle as the original is fine. with all that she now fires at 315 fps and has amazing range. a few people on here have had this work done by fire support and are all pleased with the outcome. i had extra work done on the motor cage so a eg1000s could be fitted and now the rof it great on a decent 8.4v mini battery.

hope that helps
loc

Hi Loc,

Can I ask you how much did your upgrade cost, the chap ay Close Action will fit a TM hop unit change the spring and get rid of the selector switch for £60.

Cheers

Ian

pm'd

can anyone in the know tell me what needs modifying on the tm ak hop unit to fit the mp40.
cheers
jay

I have made an Owen Gun using AGM MP40 internals.
I modified the hopup to feed from the top,could you not do the same, except feed from the side.

The Owen shoots at 324 fps with no upgrades, apart from stripping and cleaning the gearbox.

hi can anyone tell me what size the gearbox bearings are.
cheers Steve

6mm bearings