How to drill out your vertical adapter
The reason for drilling out your vertical adapter is to help with air flow. If you are going to go LP (low pressure) then you will need low pressure with high flow, that is where drilling your vertical adapter comes in. When you drill out the VA (vertical adapter) you allow more air flow making your gun flow better.
What to do: Take the VA off your gun and take off any thing and every thing attached to the VA. Now lay the VA on the table so that the part that goes into your gun is towards the left, and that the co2 tank threads are towards you. Ok, we now want to get a 3/16 inch metal drill bit. If you use a drill press the drilling will be more strait than using a normal drill, but using a normal drill will work the same if you have a steady hand. Now start drilling down into the little hole or filter where your co2 tank screws into. Stop when you see the hole coming in sideways from the valve body. They you drill down from the part that goes to the valve, to the place where you screw in your co2, be careful not to go sideways but to go strait down so you don't hit the screw holes on either side. When you are done drilling take the part and wash off all metal shavings and then dry it off and then screw the VA just the VA not attached to your gun on your tank so it blows out all the metal shavings. Then you can replace the VA back on your gun and then replace all of your regulators, expansion-chambers, and low pressure chambers. If you did hit the screw hole while drilling when replacing the screws put Teflon tape around the screw and put the screw back into the hole. That should stop the leaking. When you are done the air flow will be less constricted.