Many thanks to AyesDyef for bringing the parts down from Sydney personally and getting them machined for me.
You sir are credit to team!

Disclaimer: This mod involves using power tools therefore if you’re young, don’t know what you’re doing ask an adult to help you out, and make sure you’re wearing safety equipment.
I will not be responsible for injuries resulting from you dropping a drill on your feet or taking someone’s eye out with your darts.
I will not be responsible for any damage or breakage that may befall your Nerf Longshot.
This mod tutorial comes as is.

Without further ado let us start modding our Nerf Longshot.Below is a list of the required tools:

• Power drill or Dremel with appropriate bits.
• Phillips head screwdriver
• Flat head screwdriver
• Clawhammer
• Small Brush

First off we need to take apart the rifle.Remove the cocking handle this can be done using a claw hammer or a screwdriver with a little leverage this process should be easier the next time round.Time to unscrew the gun; first  remove the buttstock.Then remove the screws holding the gun together.

Note the tape that prevents losing screws

After you have unscrewed all the screws holding the rifle together gently ease the rifle open, don’t just pop it open as you’ll end up losing springs or the gun will explode its parts everywhere.
Notice how I’ve used some tape to hold the screws in on the other half of the casing.With this mod I removed the bipod as I wanted to use my Longshot more like a rifle than something you can deploy so it’s just matter of removing the screws and popping the legs out.
Alright below is a diagram of the insides of the gun (Thanks Captainslug for making the diagram) you need to remove the whole bolt section and plunger chamber (pictured under the diagram).Above is the plunger tube that holds the air restrictors and the air plunger itself.Unscrew these black screws, they hold the plunger in place.
Remove the plunger. At this point it’s possible for you to add in extra springs or improve the seal with a better O-ring.
But in my case I haven’t added anything at risk of putting the gun over the power rating for HvZ ANU.

Note the glue (sorry about the poor lighting)

In the bottom of the tube you will see a black piece of plastic this is the panel that covers the air restrictor and it too is an air restrictor so both need to be removed.
Some of the earlier models this part was only wedged in so no drilling was necessary but in my case they had glued it in so I had to whip out the power drill.
I used a small drill bit to make a center hole to gauge how much plastic I had to drill through, then used a 13mm bit to drill the hole and a grinding bit to clean the edges.After a bit of drilling we end up with a clean hole and if you look closely you can see the air restrictor at the bottom of the tube, pull it out with a pair of needle nose pliers.The air restrictor that was held in place by the plate should look something like the little black piece of plastic above.
You should be able to see through the tube (below).Put the gun back together.

Notice how the barrel isn't aligned properly? That was why I lost half my range during the first test fire.

Make sure all the bits line up correctly and that they fit snuggly together.
This is important as in my first test fire I though I’d lost half my range which didn’t make sense until I took apart the gun and found I hadn’t aligned the barrel properly.

Then it’s lock and load, test fire your Longshot you should get a couple of extra meters and the darts should fly straight for a bit longer.
There is a side effect with the AR gone; your darts will fishtail I have a few hypothesis as to why this happens (feel free to discuss in the comments but stupid comments will be deleted):

a) the barrel does not provide a snug fit for your darts so 100% of the air is not being forced behind your darts with each shot, the dart more likely bounces around in the barrel before leaving.

b) There is too much air and not enough barrel in my opinion a longer barrel or a muzzle brake can possibly remedy this problem (don’t use the stock barrel extension you lose lots of range and accuracy).

c) the darts themselves are not evenly balanced so the lighter tail goes everywhere while the heavier tip tries to keep a straight flight path resulting in the spin.

Anyway, if it all goes well and nothing broke you should end up with a Longshot that isn’t gimped by the air restrictors and be able to hit people a few more meters away.
Enjoy!
For those wondering where I got the sticker from it’s from the cool guys/girls at J!NX check em out here.