Punisher's Full Auto VM Mod
WARNING: Do not perform this mod if you are not well experienced with the inner workings of a VM-68! Neither Punisher nor myself can be held responsible if you screw somethig up. You have been warned!!
Here's a list, plus the secret ingredient at the bottom:
1) Cut the first O-ring and nose of the bolt off, smooth it off.
2) Remove lower plug.
3) Convert to rear cocking off the hammer. I made a full diameter delrin... erm.... handle. It's stuck out the back about 1/2" when fully forward.
*****NOTE: add a beavertail of some kind... it'll damn near knock you out!
4) No valve spring, valve at 9 o'clock.
5) File secondary sear down such that it never gets knocked off the primary.
6) HALO-B loader!!!! It's a must!
7) Two 'one-way' bearings.
These little marvels are used a lot in RC racing cars as a way to control when power is delivered to the wheels. Basically it free spins one way and locks up in the other. With a little tweeking, you can "adjust" them so that they freewheel one way and drag but still spin the other way.
I used CA glue and bonded some surgical tubing to the outer ring of the bearing so that it had traction. I made small blocks that held each bearing in the now empty cocking slots in such a manner that the hammer's sides were in contact with the surgical tubing 'tire' on each one.
When the bolt flies back, it encounters no resistance so travels at full speed. Since the plug was removed it had extra room to fly back. However, when the hammer/bolt rebounded and moved foreward the bearings attempted to lock up but only dragged (due to the modification) and slowed the hammer/bolt down. Since the main body of the hammer is slightly larger that that of the trailing sections (or my delrin cocking handle for that matter) they only dragged for a short time and then released the hammer/bolt at about 90% of the normal stroke.
The valve spring was removed to increase the dwell and raise the velocity since there's just a little less force at the valve. With this setup I was able to rattle off 5 or 6 round bursts with no problem. With a little more tuning, it could probably run continuously but I just didn't have the time to mess with it....
Food for thought....