Lightening the Stock VM-68 Hammer
The stock VM-68 hammer is a heavy beast. It's made out of stainless steel and weighs in at 9 oz. Lightening the hammer will increase the VM's cycle rate and, with some additional tweaking, can also allow the VM to run at a lower pressure and more efficiently.
Stainless steel is a very tough material so you'll need good drills to work with it. I've had the best experience with good quality high speed steel (HSS) drill bits. Don't waste your money on cheap import drills and don't spend extra on TiN coatings. You'll need to set the drill press to a slow speed. Cutting oil is a must as well. For calculating the RPMs you can use the formula 3.82 x 50 / drill diameter. For example, a 1/4" drill would be 764 RPMs. If you have a step pulley for adjusting speed it's usually better to go slower than faster. What's the 50 mean? It's a good general purpose surface-feet-per-minute (SFM) number for cutting stainless.
When drilling into the hammer make sure not to drill into the surface where the sear comes in contact with the hammer. This is pretty much the entire underside of the hammer. Doing so could cause the sear to catch on one of the holes which would make the hammer cycle incorrectly or not at all.
The hammer below went from 9 oz. to about 5 oz. I could have lightened it a little more but I wanted it to look some what clean (or as clean as it can be for a drill press job) and not hack out every last piece of metal I could. If you plan on doing this you might want to also consider buying a new aluminum hammer. Punisher's Customs, Cooper-T, and Doc's Machine have made new hammers.
I personally don't recommend going this crazy unless you really know what you're doing. A hammer this light will have a very hard time cycling reliably with the stock main spring. Cutting the main spring could help but that is an irreversible modification. Proceed at your own risk.