Weird BB behavior (curl left or down)

Discussion in 'Gun Building, Modifications & Repairs' started by Dwosky, Apr 9, 2018.

  1. Dwosky

    Dwosky Member

    75
    16
    I've recently finished my DMR ICS build and seemed to work correctly on the tests I made over short range and the chronograph, but taking it to the field I observed two issues:
    1. The first noticeable issue was that the BB curled left on long distances, the movement was like a parable, not straight. The longer it flied, the left it went. So it was kinda impossible to hit anything over a long distance. There was some wind at times, but I find weird that the BB always spun to the left.
    2. Another weird issue I had is that upon changing magazines, due to the current one being empty, the BB just flew out of the barrel and dropped dead (like if the hopup was maxed out). I had to manually adjust the hopup for each magazine change and even dropping the hopup to min didn't guarantee that the next shot flew correctly. Its like if the rubber wasn't warm and took a couple of shots to get its temperature, but I find weird this happening just at mid match, also there was like 10-12º C, so it wasn't so cold to make the rubber stiff.
    Upon the above two issues, they look to the hopup unit or rubber, but is there anything more to look for? Any idea what can cause the left curl over distance? I mean, to go up or down its kinda straightforward from the pressure of the hop, but I don't recall right now what could cause that left movement.
     
  2. Kurzciel

    Kurzciel New Member

    21
    5
    Wroclaw
    - Way too much silicon oil (imo there is no need to use it),
    - Nub position. Nubs are a little bit smaller than nub window in the chamber. Just take the chamber with nub, rubber and barrel in it, max hop up and look inside - the nub should be perfectly on the middle of the axis,

    EDIT With silicone rubbers temperatures doesn't mean anything. Don't bother this factor. Also, when you disasembly upper reciever (with chmber in it) check if the chamber is not too loose in it. It should sit tightly (when you try to move the chember with your fingers). Also, just look on the chamber when all is set - the nozzle should not be too far or too close to the gearbox (rear position - barely seen in the chamber, front position - nozzle (front) part with smaller circuit all in the rubber). I had the same problem - external barrel was turned and with that chamber also so, obviously, the nub too.
     
    Last edited: Apr 9, 2018

  3. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

    8,085
    4,616
    Minneapolis
    Clean the barrel with a solvent (not oil) and re-shoot. Clean the packing(aka "bucking") soapy water too and also re-shoot