TM Hi-Capa 5.1 GM build and random fps

Discussion in 'Gun Building, Modifications & Repairs' started by Herby, Jan 30, 2019.

  1. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

    Batch manufacturing to "no standards", that is Guarder. Sometimes good, sometimes all varies.
  2. link0

    link0 Well-Known Member

    SF Bay Area
    The Guarder BBU also sucked for me. Caused endless problems until I just went back to the stock TM BBU.

  3. Calikuhl81

    Calikuhl81 New Member

    San Diego
    Hello, I've recently had the same problem with my TM GM, and I read your suggestion for the Teflon tape. I added that around the bucking/inner barrel and put it all back together, re chronographed it and viola, my pistol went from 235.8 to 287.3, that's a 51.5 fps improvement!! Thank you
  4. Ben3721

    Ben3721 Well-Known Member

    One should be aware of a pretty bad flaw in TM pistols, the top of the packing where the hop leaf arm sits is unsupported by the hop up unit block. This causes a leak every shot between the packing and barrel. Some packings are tighter and may help this leak, but one can seat the packing and run a thin line of glue for a semi permanent seal, to remove it, you'd have to ruin the packing. Less than an ideal fix, but I'm pretty ocd and this assures a more definite fix than expanding the packing by packing Teflon tape under it, unless it's undersized/loose to begin with.

    Another thing is mags moving loosely in some aftermarket grips, the mag holds the value and the seal to the nozzle. Both very sensitive aspects to consistency, there are ways to shim that if one cares enough.

    Lastly, don't use green gas and expect performance. Use thick grease lightly inside the nozzle every once in awhile if the nozzle binds. Obviously lube the slide rails and sears once in awhile too.
  5. OPairoft

    OPairoft Active Member

    Use silicon sealant, doesn’t ruin the packing and is very easy to remove from the barrel/packing yet still seals 100%.
    Ben3721 likes this.
  6. GrimWolf0770

    GrimWolf0770 Active Member

    Pittsburgh area
    That seems like alot of parts to get working in one gun........