
Here's your basic MagStrike Dart Tag edition. The Iron Man 425 is exactly the same inside, just different color plastic.
Step 1: Remove all screws, including the 2 in the orange pump handle, make sure you don't miss any of the ones in the black bladder enclosure portion of the gun.
Should be a total of 21 screws, but if you get less or more, don't worry as long as the gun comes apart. The rear of the bladder enclosure has 2 pegs in it, be careful when pulling apart so you don't snap them off.
One note, if you're not planning on painting the thing, you don't actually have to remove the pumping handle, so a step saved if you're not planning on painting.

Step 2: This bit is annoying. You have to take a small screwdriver or other flat object and pry off the bit covering the pumping lever so that the two sides of the shell can come apart.
Technically you can pull the shell apart from the rear and this piece should pop off, but I prefer the screwdriver method. Any nicks you make can be sanded down later before the painting and/or reassembly.

Here's your opened Magstrike, all the bits that come off in the disassembly stage are off.

Here's the bladder assembly close up, the four screws towards the front hold the front of the bladder closed on the cap that connects it to the rest of the gun, the round cylinder is there so that the bladder doesn't contact anything sharp while inflating.

This is the over-pressure release valve. We want to get rid of this so that we can pump this thing up to 2-clip levels.

This is the firing action, the mechanism is why there's no point in trying to increase the overall air pressure coming out of the bladder, just the capacity for air volume. Making the air pressure higher will just make the gun fire faster, not any further.

This stupid thing is the trigger lock. We're getting rid of it.
Step 3: Remove the two screws holding the upper green piece in place and remove all the bits attached to it.

And now you have an unlocked gun, just means you an pull the trigger without a clip in place, feel free to skip the previous step if you feel you need a trigger lock, it's not going to affect anything in the long run.
The bit you see above with the small green tab is the clip advancer, it's the bit that actually shoves the clip upwards during firing.

There's the trigger lock mechanism, if you're interested.

Step 4: Remove 8 screws from the bladder clamp and bladder protection mechanisms.
Make sure you keep an eye on which screws came from where, they're different types.

Step 5: Remove the bladder from the front plug.
Here's your fully disassembled Magstrike, ready for bladder modification. If you're painting you can pull out the rest of the guts now, including the trigger+spring, if not just leave everything in place, there's nothing you can do to the rest of the system to make it work any better.

Step 6: Unscrew 4 screws from the rear plug clamp assembly and set aside.

Step 7: Pull the cap off the overpressure release valve.

Step 8: Remove the valve mechanism, discard valve cap and valve mechanism, they will not be needed.

Step 9: Remove the rear plug from the bladder and insure that it is free of debris.

Step 10: We'll be filling the end plug with hot glue, so place some sort of tape over the end hole so that your plug doesn't stick to the table.

Step 11: Turn the plug over and fill with hot glue.

It should end up looking something like this, allow to cool completely before re-inserting into the bladder.

Here's the end of the plug after being filled with hot glue, the next step is optional, which is why I didn't put it before the hot-glue portion of the process.

Step 12 (Optional): To give the bladder more horizontal movement space, take a hacksaw or other cutting tool and chop off the nub on the end of the plug.

Step 13: After the hot glue has completely cooled, take some liquid nails or other silicon based glue and place a generous amount around the ridges of the rear plug.

Step 14: Place the plug back into the rear of the bladder and make sure it slides completely in to place. Use your finger to wipe away any excess glue.

Step 15 (Optional): Take the rear bladder clamp and cut it where pictured, I prefer this method as it allows for the maximum horizontal travel of the bladder, but it is up to you if you want to do it this way, make sure you leave space between the plug and the bladder for the rear piece to slot in if you choose to leave it on.

Step 16: Take your liquid nails and apply a glob to the inside of both sides of the rear bladder clamp.

Step 17: Screw the rear clamp back in place where it was previously on the bladder and place it in a clamp to dry. Allow to dry a minimum of 24 hours before removing the clamp.

Here is your completed bladder modification. If you wish you can add some more liquid nails around the outside of the area between the clamp and the rear plug.

Here's the two types of screws that came out of the bladder section, the lower screws came from the clamp and the upper screws came from the protection cylinder. You can tell the difference by the thread density. Make SURE that the correct screws go in the clamp or it will most likely rip itself out of the plastic.

If you're painting, hold off on this step until you've completed your paint job, if not, go on.
Step 18: Re-Attach the clamp by inserting the screws diagonally, lower right, upper left, lower left, upper right. Tighten them about 1 turn at first, and then tighten them all the way once all 4 are in place.
At this point you're done, you can replace the top of the bladder protection cylinder and then screw the shell back together and you have a working, modified MagStrike.
MagStrike Clip Modification

Here you have the stock clip on the right, and the clip with the cap removed on the left.
Step 1 : Remove 6 screws from the top of the clip and place the cap and belt-clip aside.

Step 2: Drill or Dremel out the air restrictors, they are part of the barrel assembly, so you'll have to be careful not to damage anything else while you're doing this.
If you're not replacing the barrels, then you're done, the clip can now fire Stefans and will fire a bit further. Just replace the top bit and you're all set.

A view from the front, there's not a whole lot of difference, but the airflow change makes it all worthwhile.

If you're replacing the barrels with PVC or PETG then continue on.
Step 3: Remove the back plate from the clip.
This is an EXTREMELY fragile piece of plastic, so you must be very careful not to damage it in the process of removing it. I took a dremel with a plastic cut-off wheel and trimmed down the edge of the clip around the outside of the plate and then slid an X-Acto knife underneath to release the glue. Do not pry or yank at the plate, it will bend and your clip will be screwed.

Here's your clip with the back plate removed.
The Iron Man 425 clip looks a little different, the secondary plate underneath the backplate doesn't exist there, the barrels are just attached to the sides of the clip and the plate is glued to the barrels.
Either way, the next thing to do is ditch those barrels.

It's up to you how you do this, as you can see it can get a little bit messy.
Step 4: Remove the existing barrels in preparation for PETG or PVC.
If you're using PETG you can try to leave the secondary backplate in place for extra reinforcement, but that's up to you.
I took a dremel cutting bit and ran it around the outside edge of the clip between the barrels and walls, the barrels are attached to each other and each one is attached to the wall of the clip, it's slow going but it works.

This was my first attempt at a clip mod with the Iron Man 425 clip, as you can see I got a little bit frustrated with it and took a hammer to it. The backplate is a little bit bent and I'm going to have to take a little heat to it so that it settles back in place nicely.

Step 5: Place the back plate in a clamp and glue on the barrels
Here you see the backplate clamped in place an 3" PETG segments lined up ready to be glued.
I put a small glob of hot glue on the top of each, letting it flow around and cool, then moved the backplate up in the clamp and did the bottom row the same way.

Here's the second row of barrels in place.
If you're overly generous with the hot-glue during this process you may need to do some trimming before you replace the barrel holder on

Here's the back of the reassembled clip, you have to be absolutely sure that the back plate is is flush and flat so that the clip can move freely through the gun.
I just used a small amount of Zap-A-Gap around the edge of the plate to hold it in place, making sure to wipe any drips off so that the back plate remained flat.

The front of the reassembled clip. You can put some more hot-glue down there if you want just to make sure of the barrel seals, but it's not required.

Side view, you can see where my dremel cutting bit came through a little bit, there isn't a whole lot of wall plastic there and the bits holding the barrels to the walls are pretty thick.

The third clip I did turned out much easier than the other two, this one just required that I put a small screwdriver in the gap between the plate and the clip at the top of the clip and pry gently. Much easier than the dremel option. Of course this also means that the barrels are going to be much more of a pain to take out.

You can see that there's a LOT less glue on this one compared to the last one, which is why I could just slide the small screwdriver underneath it and gently pry the plate off.

Here's the first clip I modded after I painted it gold to go with the Iron Man color scheme I cooked up for the 425.
The barrels are slightly uneven in length mainly because I use a hand hacksaw and that's not exactly the most accurate tool in the world.
I hope you enjoyed my MagStrike modification guide, I'm always happy to take suggestions and constructive criticism.
You can find my Flickr based guides and a bunch of pictures here: Nerf Pictures and Writeups