rebuilding my m4

Discussion in 'Gun Building, Modifications & Repairs' started by jedimind, Nov 10, 2012.

  1. jedimind

    jedimind New Member

    hey guys i have a very, very old classic army M15a4 and after five years of play its beginning to give me low and inconsistent FPS. also at the last game the gun stopped firing and the lipo was swollen and hot...i am not sure if it was the cheap battery or if it was the wiring in the gun.
    i'm new to teching on airsoft, but not tinkering in general so i am confident. tonight i took the gearbox down and observed a lot less wear than i please bear with me and help me decide if my todo+shopping list is adequate to bring this gun back to life:

    clean & polsih gearbox & cylinder
    rewire gearbox & install mosfet (i'm looking for a simple mosfet to make trigger assemlby more reliable)
    correct AOE, adjust motor height, and shim (in this order, yes?)
    stabelise the inner barrel

    tentative shopping list:
    new wiring w/ a fuse and dean's connectors - i'm looking for the most reliable option here, any opinions on brands or types of wiring? any good tutorials on the best way to go about re-wiring the gearbox?

    lipo batteries - i am into reliability over rate of fire, so a lower voltage is fine, higher mAh is more important to me

    mosfet trigger replacement - looking for recommendations, reliability is most important

    shims - i just need a good bag of shims to tune it up

    spring guide bearing - is this necessary if my goal is to be 400fps? do i need a new spring guide to add a bearing

    piston / piston head - the only wear i really observed were in the pistons plastic teeth so i might wanna new one...what brands are recommended? are bearings on the piston head needed at 400fps? and do you guys buy sorbo pads or cut them out of mousepads?

    cylinder head - my cylinder looks cool but the cylinder head is old and covered and crap...should i try to clean it or are they cheap / worth replacing them for something new?

    i don't think i'm going to replace:
    gears -- they looked fine...worth upgrading?
    spring guide -- unless the bearing helps consistent fps a ton...which i've heard it helps
  2. Ehudakineyah

    Ehudakineyah New Member

    Idk what's going on, but my reply's don't show up on here :/ sad face

  3. Lefse

    Lefse Well-Known Member Supporting Member

    Any stock parts that are intact and has little wear can be re-used. Your to-do list seems pretty thorough to me, standard full overhaul. If you need to replace anything, you can't go wrong with Lonex parts. Make sure you glue the bushings in properly, it will help keep things reliable. A bearing spring guide is a good idea. Installing a mosfet and Deans connector is also a good idea. This will not just increase reliability, it will have positive effect on the performance of your gun too. Take a look at to find a new li-po pack, they have tons of different packs, so you're guaranteed to find a suitable one.

    Some motor maintenance might be a good idea too. Clean out all the dust with compressed air, and sand the commutator with very fine grit sand paper to remove any carbon buildup.
    Last edited: Nov 11, 2012