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Dboys M4A1 & cutting a slot in the cylinder as possible downgrade ?

  • 11-07-2011 5:00pm
    #1
    bullets
    Registered Users, Registered Users 2 Posts: 4,612 ✭✭✭


    Have some guns sitting in the wardrobe since possibly since 2007
    that are inconstant firing, all bought from Irish retailers.

    one of them a Dboys an M4A1 was shooting anywhere between
    190fps to over the limit at 350-360 fps. With hop up off,
    So decided a spring swap was the
    first thing to do to bring it back to firing within the limit.

    I thought the nozzle may have been drilled in an attempt to downgrade it
    but I checked it and its fine. I assumed the wild inconsistency was due to airleaks and the spring may have been too strong for the legal limits here.

    Stripped it down completely today including the hop up unit etc, and changed the spring to a deepfire M100 spring (Shop only had that one so could not get a weaker one) its about a coil or two shorter than whatever spring was in the gun stock.

    Re-greased everything (It was swimming in grease even after sitting about
    for years) Cylinder/piston compression was fine! shimming was not too bad, only added one/two shims, Plastic bushings was a surprise and I had no spares to change them. The Motor feels a little weak when I turn it compared to another M4 I had only stripped the day before. Anyway
    everything goes back together is it fires at a very consistent 290 with full hopup. Only problem is its firing at a very consistent 360 with hop up off! :mad:

    The cylinder is the non-ported type. I was thinking about maybe taking a demel and cutting a small port at the same place you see on
    ported cylinders either that or cutting a coil or two off the spring.

    Anyone got suggestions ? (I suppose the easiest thing it go off and buy another spring...again)

    At least the inconsistency between shots has gone away.
    ~B


Comments

  • #2
    Shidosha
    Closed Accounts Posts: 44 ✭Shidosha


    If it's firing consistently now, wouldn't cutting or drilling just risk it getting all random again?

    It really sounds like you just need a different spring. I'd start off by trimming your current spring a little at a time and testing after each cut to see if you can get it firing consistently at 320-ish with the hop-up off. If you find that it keeps consistent but you can't get it down low enough, it's definitely time to buy a new spring.

    Pretty sure too that it needs to be firing legally with the hop-up completely off.


  • #3
    bullets
    Registered Users, Registered Users 2 Posts: 4,612 ✭✭✭bullets


    Shidosha wrote: »
    Pretty sure too that it needs to be firing legally with the hop-up completely off.

    Yep! unfortunately it does.
    Just wish more guns came with a motor cage! where ya dont end up needing
    to take the pistol grip off and on every time to check it!
    (or better still the quick change system like some guns are sporting now)

    ~B


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