You drill in the center-bottom of the short mags, or if you have a long mag you do it in the cylinder that has the gas port (disassemble the mag and unscrew the cylinder; it'll make life a whole lot easier). Tapping is the process by which you add threads to the inside of the hole that you just drilled, and deburring is running a small circular file around the edges of the hole (inside and outside edges) to make sure that they're not sharp and that there isn't any flash metal that could break off and lodge itself in a random o-ring.
It is actually really no big deal. You really do need to read Brainplay's guide, though. It has step-by-step instructions on how to do this, from the drilling of the mag all way through building the external rig. It even has pictures that you can follow quite easily while . If you're buying a ready-built one from Palmer's, then congratulations, your work load is cut in half, but the mag drilling part of the guide is still applicable.
I'll make it super-easy. This is the part that applies specifically to you.
Drilling and TappingTools Needed
1 Hand drill or drill press
2 blocks of wood *note: only needed if using a hand drill
1 C-clamp *note: only needed if using a hand drill
1 Phillips screwdriver
1 adjustable wrench
1 1/8 - 11/32 tap *note
the tip starts at 11/32 and expands out to a full 1/8
1 11/32 drill metal drill bit *note NOT A 1/8 DRILL BIT
1 can of tapping oil or spray on silicone based oil (you can use airsoft gun lube just fine)
-1 1/8 gas fixture *Since the metal is soft and will warp if repeated screwed/unscrewed I prefer to have a fixture which gives me more flexibility for future addons. If you screw an airhose directly into a magazine it will work fine but you might have other ideas for later. Fixtures can be found in any hardware store, are made of brass, and cost $1 or less. Its best to ask for SEAMLESS fixtures although most usually are already.
-teflon tape of loktite sealing adhesive
The first item of business is to disassemble the magazine. If you look at the back end where the striker plate is located you will notice 4 screws.
Remove these screws and keep them in a safe place. You don't want to lose them. Next you will remove the backplate. The backplate is NOT glued to the magazine. Instead there is a rubber O-ring inside sealing it from the inside. It will take a bit of pressure to remove the backplate but there aren't any loose pieces that will just fall out (if there are when you pull yours out it might have been damaged). Check the 0-ring for any damage or just wear and tear. Below is a picture of what the backplate and arm look like. The little arm at the end should be sitting in an L position when you replace it. REMEMBER THAT!
Now if you're using a hand drill and I imagine many of you are then you'll want to secure the magazine with the wooden blocks and C-clamp as shown in the picture below. The blocks have to be of the same size of course to ensure an even area. If you look at the picture closely you can see some small dents. These were pilot dents which are where I'll start drilling. Most people drill straight down the middle/center of the magazine but I decided to go a bit more towards the back where the backplate is located.
This part was optional but its still good for those inexperienced in this type of work. From the pilot dents I started my "pilot hole". The pilot hole is basically a smaller hole that will be used as a guide for the larger main drill bit. This isn't necessary but it makes it much much easier to drill later. Since the pilot hole is smaller I can afford to expand it out a bit more if I screw up and drill at an angle in order to fix such a mistake. It also makes it easier to drill with the larger bit. As you can also see I'm cheating since I have access to a cheap drill press.
*The magazine is made of thick aluminum. This is a soft metal so you will want to drill slowly. Putting alot of weight and pressure while drilling leads to the bit becoming caught in the metal. This of course can make you loose control of a hand drill which can damage the drill bit. And while rare occurance a broken drill bit lodged in your magazine is not a good thing. Slow and easy may take longer but it keeps you from having accidents and it lets you keep that the angle is being drilled straight.
**Note: While the can looks similar that is NOT
WD-40 being sprayed on the hole. WD-40 should be kept away from your rubber O-rings.
Here is the actual hole being drilled using the 11/32 drill bit. The smaller pilot hole will keep it straight and make the drilling go alot faster since there is less metal to deal with. Once the hole is completely drilled you'll want to deburr the edges. This basically means removing any bits of metal or sharp edges around the entry and exit holes.
Ok you've got your hole drilled. Now comes the truly important part of tapping the threads into the hole. The tapping doesn't necessarily have to be 100% straight to be functional. However, it will eliminate any future problems that may arise due to one side having shallower threads.
First take your tap and insert it into the hole. Line it up as best and you can and then with hand pressure alone try to twist the tap into the hole. This will lock it into place and you can really check the angle of the tap in the hole. Align as necessary. Once its aligned and you have once again used hand pressure to secure it in the hole its time to break out the wrench. Attach it to the top of the tap as seen in the picture below. While holding it steady give it one full rotation. Check your alignment. If its off a bit you can back the tap out of the hole and retry. Try to keep the retries to a minimum. A few won't hurt it really since you'll be really biting deep into it once you screw it in deeper. Its best to have a slightly slanted hole than a dozen tries which have chopped up the hole walls badly.
Start more rotations. Now that you've started to bite into the metal you can remove the small wrench and throw on something larger (I pulled out a medium sized monkey wrench) to help you rotation the tap easier. You'll need to rotate the tap all the way to the end of the thread blades.
*note: when cutting the threads its best to go forward a little bit then back up a hair. Puuuuuussh, back up. Rinse and repeat.
Remove the tap by backing it out the way it came. Check the edges and deburr and necessary.Congradulations, you have a tapped magazine
. The rest is easy.