Page 8 of 11 FirstFirst ... 4 5 6 7 8 9 10 11 LastLast
Results 71 to 80 of 104

Thread: MG47-308

  1. #71
    Gunco Member alpine44's Avatar
    Join Date
    Feb 2009
    Posts
    76
    Feedback Score
    0

    Default

    Mustang03

    Here is one way to add a cool 68% force to your gas system: The original gas piston is 0.550 dia. You can fit up to 0.712 dia trough the RSB with very minimal Dremel touch up.

    This will give you a force increase of about 68%. I will send you pictures of the M77 adjustable gas bushing on Monday. A bushing like that could be used to couple a larger gas tube to the existing gas block.

    Do not weaken the spring. You may need that force to get through the forward feeding and locking stroke reliably.

  2. #72
    SHARPSSHOOTER5090 SHARPSSHOOTER5090's Avatar
    Join Date
    Jul 2007
    Location
    Utah
    Posts
    366
    Feedback Score
    5 (100%)

    Default

    Capt. V/Mustang

    On my original MG47 prototype I made a gas tube out of a section of a 12ga. barrel and a piston to fit. I did have to slightly open up the RSB to get the larger piston to pass through. Then with a very tight gas tube to gas block joint, I had just a little too much force. The BC would slam back into the butt stock, which was also the BC stop, with enough force that it started to egg out the butt stock attachment pin holes. I then drill some gas relief holes in the gas tube but it still gave me more that enough force to actuate the feed get full stroke from the BC and operate the feed cam. An adjustable gas block would be a nice feature.

    SS

  3. #73
    Gunco Member alpine44's Avatar
    Join Date
    Feb 2009
    Posts
    76
    Feedback Score
    0

    Default

    12ga bore diameter is 0.729". That will give you a 76% force increase over the stock piston.

    This larger piston diameter plus an adjustable bushing should do the trick for different loads.

    (BTW: Just got the info that a M60 piston diameter is 0.871" but this one bleeds some gas out of the front of the gas tube. I think somewhere between 0.700" and 0.730" would be fine for the M47-308)

    Please be patient with me getting the photos from the M77 bushing. I got transfered for a couple of years to the Socialist Republic of Massachusetts where all guns require permit from local authority. No thanks! I rather "board" my toys out of state.
    Last edited by alpine44; 02-20-2009 at 05:08 PM.

  4. #74
    Gunco Member MustangO3's Avatar
    Join Date
    Jun 2006
    Posts
    150
    Feedback Score
    0

    Default

    You guys are right on track on what my issue is. I used a 3/4 black pipe for the gas tube and it is just blowing by once the piston unlocks. I will either redo the gas tube or weld a bead around the piston to increase the pressure. I took it out today and had it fire correctly two rounds in a row, bur that was it. Additionally for the first time today, I had an extraction problem. I'll take it apart later, but I believe it all has to do with the poor cycling.



    Last edited by MustangO3; 02-22-2009 at 09:52 PM.

  5. #75
    Gunco Veteran [486]'s Avatar
    Join Date
    Dec 2008
    Location
    MSP area, MN
    Posts
    1,631
    Feedback Score
    0

    Default

    You could try cutting flutes in the sides of the piston, with the old gas tube, sort of like the "washer" thing right behind the piston head on a galil...

  6. #76
    SHARPSSHOOTER5090 SHARPSSHOOTER5090's Avatar
    Join Date
    Jul 2007
    Location
    Utah
    Posts
    366
    Feedback Score
    5 (100%)

    Default

    What links are you using? MG34/42/53 linked or disinigrating type? RTG has the latest MG3 feed pawl that is supposted to work with both types. The different types of links have different pitch than each other and if you are using disinigrating links it may be part of your feed problem, besides lack of stroke. Labrinth grooves on a piston head only work if you already have fairly tight clearances. They cause turbulance along the sides of the piston which in turn causes a slight bit more sealing but if you have too much clearance already they won't help.

    SS

  7. #77
    Gunco Member TheRedHorseman's Avatar
    Join Date
    Nov 2004
    Posts
    46
    Feedback Score
    2 (100%)

    Default

    What are the dimensions of the tube that you'll need? I'm starting to dive into this madness myself and could turn a bit of extra tubing for you while I'm at it on the lathe.
    Hated by many, loved by few.

  8. #78
    Gunco Member MustangO3's Avatar
    Join Date
    Jun 2006
    Posts
    150
    Feedback Score
    0

    Default

    yes, I have too much clearance, but I'll play with it more. it's getting there.

  9. #79
    Gunco Member cntrailrider's Avatar
    Join Date
    Nov 2004
    Location
    El Paso Texas
    Posts
    255
    Feedback Score
    0

    Default

    Seal that gas system tight! 3/4 of the problems with all MG47's built to date have been insufficient pressure to cycle. Tighter the gas tube, the more likely it will work. I know!

    Steve

  10. #80
    Gunco Veteran [486]'s Avatar
    Join Date
    Dec 2008
    Location
    MSP area, MN
    Posts
    1,631
    Feedback Score
    0

    Default

    But his was beating the back of the rear trunnion's holes to egg shapes, so I think that less gas is needed [with your older gas tube]...

Page 8 of 11 FirstFirst ... 4 5 6 7 8 9 10 11 LastLast

Search tags for this page

mg47 belt fed plans
,

mg47 build

Click on a term to search our site for related topics.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •