Friday, March 26, 2010

Nerf Magstrike Mod - Air Compressor System!

The Nerf Magstrike has proven to be a popular high RoF blaster amongst Nerf players. It has a comfortable form factor, uses a clip-based ammo system, is powered by compressed air and can fire in both full-auto and burst-fire.

But even though its air bladder can be modded to hold more air volume to fire more clips at a time, there is still a limit to that function, not to mention all the physical effort required to manually pump it up!

The solution = Air Compressor Mod!

Disclaimer: Modify at your own risk. Modifications may wear out or damage your blaster. Please be careful when using hobby tools!

Lets begin...

Air Compressor Mod

Step 1: Obtain Pressure-rated Air Hoses, Air Hose Couplers and Tire Valves. In the photo below, i've displayed the various components that can be used.

Tire valves can be sourced from car workshops or garages.

The transparent pressure-rated air hoses are 6mm OD / 4mm ID in dimension, exact match for the original Magstrike air hoses.

I usually use 2 types of air hose couplers for my mods, the transparent ones are nylon barbed tee or splicer air hose couplers, these will require additional clamping or epoxy glue to secure them to the air hoses.

The black-coloured air hose couplers are special tee or splicer air hose couplers that feature a quick-release system. Just insert the air hose in to engage the automatic internal clamp and air seal. To detach, just press the blue plastic collar to release it.

Pressure-rated air hoses and couplers can be sourced from pneumatic equipment manufacturers and suppliers.

In this mod, i'll be using the quick-release air hose couplers so that the system can be modular.

Step 2: Obtain a Portable Car Tire Air Compressor, a 12V Sealed Rechargable Battery, a 12V Plug Adaptor and a set of Electrical Cables.

Portable car tire air compressors can be sourced from car workshops or garages.

The 12V sealed rechargable battery, 12V plug adaptor and electrical cables can be sourced from electronics or hardware stores.

Step 3: Open up the Magstrike. Make sure it is a fully working unit without any air leaks.

DO NOT remove or plug the over-pressure valve (OPV).

If the OPV has been disabled, DO NOT perform this mod until its enabled or properly repaired.

When the Magstrike is connected to an air compressor, the OPV will act as a constant safe-guard to prevent over inflation (and resulting rupturing) of the air bladder system by releasing excess air pressure, it has to be functioning properly to avoid damage to the blaster (or user).

Step 4: Cut the air hose between the air pump and air bladder system. Remove the original air pump.

Step 5: Connect the air hose and quick-release splicer air hose coupler.

Step 6: Attach the air hose to the tire valve using 2-part epoxy glue, make sure the glue fills all the gaps but yet does not seep into the connection to ensure an unrestricted air-flow.

In my example, i used a smaller section of air hose connected to the tire valve, for modular design, and connected it to another quick-release splicer air hose coupler.

Connect the tire valve to the air compressor, which is in turn linked up to the 12V battery.

Test it out to check that everything is working properly, the air bladder should fill up and stay filled for an extended period of time, any decrease in pressure will indicate a leak somewhere in the system.

For those interested to know, the air compressor i use has an in-built pressure gauge, so i can track that the air bladder at full air volume (without the white retaining shell and after the OPV activates) is operating at around 50-60 PSI.

Alternative Step: The air compressor system can also retain the original air pump. Just use a tee air pressure hose coupler instead to connect the air bladder, air pump and tire valve.

Note that with this alternative method, due to the limited space between the air bladder and air pump, the air pump may require some additional adjustments in positioning within the casing, including some trimming of the casing to create an exit opening for the tire valve.

Step 7: Assemble the Magstrike casing... and its done!

Add-on Step: To fully automate the air compressor system, install an automatic "cut-off" switch to the air compressor's electrical circuit.

I used a "push-to-off" switch which can be sourced from electrical parts supply stores. When the air bladder fills up and expands to a certain size, its OPV plastic assembly will press onto the switch, thereby switching off the air compressor. When the Magstrike is fired and the air bladder decreases in size, the switch will then be released and the air compressor will resume pumping air. This system regulates the air compressor to automatically pump air only when required.

Ammo Clip Management

With all that continuous supply of air pressure, the Magstrike will now need ALOT of clips.

Magstrike clips are much larger than N-Strike clips though... so how to carry them efficiently?

To solve that issue, i customised an Ammo Clip Belt System which consists of a thick nylon tactical belt with adjustable "dump" pouches that fit the Magstrike clips.

Harness System

I'm not keen on the idea of tethering cables or hoses from waist pouches or backpacks to blasters, i've found that method ungainly and too restrictive. Loose cables tend to get tangled up easily, especially when quick response and fast movement is required during games.

So i customised an Air Compressor System Harness to mount the entire system onto the Magstrike itself. Therefore, a Magstrike with the air compressor system can now become a completely stand-alone unit, which offers the best combination of flexibility and mobility.

Overall, the entire air compressor system (incl. battery) adds around 1.3kg to the Magstrike. It is abit heavier to carry, but i managed to adjust the weight distribution for equal weight balance between both harness pouches, so the blaster can still be held and fired comfortably.

Ready to go!

Test Fire & Demo Video

Yeah, i know... the air compressor is quite a noisy piece of equipment! :)

Tuesday, March 23, 2010

Nerf Longshot "Brass Breech" Mod Guide!

This mod guide will look into my "Brass Breech" modification for the Nerf Longshot.

It is based on the original "Angel Breech" design.


Just a quick background on the origins of this breech design, the original "Angel Breech" design was created by forsaken_angel24, and he posted his guide on how to make his original version on the NerfHaven forum.

Link to the original "Angel Breech" Mod Guide by forsaken_angel24.

Full credit goes to forsaken_angel24 for his original breech design!


The stock Longshot plastic breech does not have an air-tight bolt to barrel seal, hence the plastic bolt itself is essentially the barrel. Once the foam dart is fired out the bolt, the foam dart already starts losing power and velocity. In addition, most of the air pressure from the plunger is wasted once the foam dart leaves the bolt.

The design objective of an air-tight brass breech system is to create a 100% air-tight seal all the way from the plunger through to the barrel, thereby providing efficient air pressure delivery to propel the foam darts further.

This would result in more power within each shot, with greater firing distance and faster dart velocity.

The "Angel Breech" was originally designed to chamber shorter foam darts (commonly called "Stefans", DIY foam darts made from foam backer rod).

I have tinkered with the part dimensions and worked out a new set of measurements to allow the "Brass Breech" system to chamber standard-sized foam darts too.

In addition, i've added a "bolt half-pipe" design into the breech system to create a larger adhesive contact area for the bolt sled attachment piece, creating a much stronger attachment point (very essential for Longshots using stronger springs).

The following guide will cover my customized version of the "Brass Breech" mod.

Important Note:

The "Brass Breech" mod is a more advanced mod project that should only be performed by those who are already familiar with modding the Longshot.

For new modders, please refer to the Nerf Longshot Mod Guide to get familiar with the modding basics first.

Disclaimer: Modify at your own risk. Modifications may wear out or damage your blaster. Please be careful when using hobby tools!

Lets start...

Step 1: You will need to obtain 4 different sizes of brass tubes (Brand: K&S Engineering).

The brass tube sizes are: 1/2", 17/32", 9/16" and 19/32". All of them are 0.014" wall thickness. They are usually supplied at hobby shops in either 1 ft or 3 ft length tubes.

Oxidization tends to occur in store bought supplies, so give the brass tubes a good polish with some Brasso Metal Polish, polish both externally and inside the tubes, this helps smoothen out the surfaces for lower friction.

Shiny things are always nice and it'll give your blaster some "bling" too! :)

Step 2: We will work on the barrel and bolt receiver first.

In this example, i'm using 1 ft of 9/16" brass tube for the barrel.

Take a Rotary Tool with a cutting wheel, and cut a 8 cm length bolt receiver half-pipe in the 9/16" brass tube.

Use a sander bit to round out the edges and corners.

Please be careful when handling such hobby tools, wear protective eyewear, dust masks and gloves.

Step 3: To help the chambered darts achieve an even tighter air seal, make tightening rings in the barrel.

Use a Rotary Pipe Cutter and create the tightening rings. Just tighten the pipe cutter slightly around the brass tube, then rotate. Do it a few times to create the tightening rings.

Okay, thats all for the brass barrel and bolt receiver, you can put it aside for now.

Step 4: We will now go on to the bolt section of the breech.

Separately cut out a set of brass tube sections in the following lengths:

1/2" brass tube: 11 cm
17/32" brass tube: 2 cm
9/16" brass tube : 2 cm
19/32" brass tube : 17 cm (5.5 cm for bolt half-pipe)

These are my custom tube measurements for a breech system that can chamber standard-sized darts. In addition, it also features a more secure "half-pipe" bolt attachment point design.

The measurements need to be as accurate as possible. Any variations may affect the overall structure and air seal of the breech system.

Step 5: Cut the original stock plastic bolt until around 1 cm of the plastic bolt is left.

Nest all the 4 brass sections for the bolt completely into the plastic bolt end-piece.

Here is my Nested Brass Tubes Cut-Away Diagram:

Use the strongest glue you can get to glue everything together. I use "Selleys Super Strength" 2-part slow-curing epoxy glue (and it actually requires a curing time of 3 days!). Make sure the glue cures completely for maximum bond strength.

Completed nested brass bolt assembly.

Nested brass bolt internal assembly.

Test fit the bolt section with your barrel and bolt receiver, place a dart into the breech system to test the dart fit too.

Step 6: Once the brass bolt sections are permanently attached, fill up the deadspace in the plastic bolt end-piece hollow space with hotglue (or any other suitable filler material).

Step 7: We will now need to do a test alignment of the various components.

Secure the brass barrel inside the original orange plastic barrel by wrapping it with electrical or duct tape to temporarily widen it's outer diameter, so that the brass barrel can be wedged tightly inside the plastic barrel, yet still movable to allow adjustments for test fittings.

Check all the part positions and make sure that a clip with a standard-sized dart can fit nicely into the breech opening.

Note that the 19/32" brass bolt half-pipe will slide over the 9/16" brass barrel half-pipe, which in turn slides into the brass bolt assembly.

Step 8: To attach the brass bolt to the bolt sled, we will need to cut out the attachment piece from the original plastic bolt.

Position the brass bolt, attachment piece and bolt sled in the casing and note the maximum forward and backward movement of the bolt to find the correct point to attach the plastic attachment tip to the brass bolt.

Note that a segment of plastic behind the attachment point has to be trimmed thinner so that it can slide into the plunger casing properly. Just whittle it down until it fits.

Use some sandpaper to roughen the surfaces on the plastic attachment tip and brass bolt, then use the strongest glue you can get to glue the 2 parts together. Again, i use slow-curing 2-part strong epoxy glue here too. As always, make sure the glue cures completely for maximum bond strength.

This is the section that has to take the most load, especially when stronger springs are used.

Step 9: Assemble everything together into the casing, note that the pop-up blocker plate mechanisms are all removed, we don't need those anymore.

Step 10: Test your "Brass Breech" Longshot!

Breech open.

Breech closed.

Ready to go!

Nice and shiny! :)

Sample Test Fire Results:

PTG: Parallel-To-Ground (Shoulder height, no elevation)
ATG: Angled-To-Ground (Aimed higher, 30 degrees elevation)

Distance is measured at where the dart lands (Average of 6 darts).

Brass Breech Longshot (14kg Load Spring)
Ammo: Customized FBR foam + 1.1 gram soft silicone tip weight
PTG = 110-120 ft
ATG = 140-160 ft

Note that the test was done indoors with customized foam darts and the results are sample estimates for reference (your results may differ depending on materials and mod techniques used).

Average Shot Velocity Measurement From Shooting Chrony F-1:

FPS data are from an average of 12 recorded shots.
All test shots are fired with the blaster barrel muzzle approx. 6 inches from the 1st sensor.
Tests are done indoors with natural light sources.

Important User Tips:

- Clips must be loaded only when the breech closed. This is so that the clip feed-lips can "catch" around the brass bolt for a proper fit.

- For smooth dart chambering process, make sure that foam darts used are no more than 7 cm in length.

- The better the foam dart fit in the brass barrel, the better the range results.