Doomsayer "M4 Shoulder Stock" Mod!

The following write-up will look at changing the ERTL Rapid Fire Shotgun (RFSG) original kid-sized brown shoulder stock to a more practical M4 shoulder stock.

For those who are keen to know more about Doomsayers (modded RFSG), you can read the original mod guide by Forsaken_angel24 at the NerfHaven forum:

http://nerfhaven.com/forums/index.php?showtopic=9845

Note that there are many methods to do shoulder stock mods on blasters, this isn't the only (or best) way, its just something i tested and worked.

Step 1:

Get your choice of replacement shoulder stock. In my case, i got a plastic replica adjustable M4 shoulder stock.




Step 2:

Use a dremel or handsaw to cut away the back portion of the RFSG, in my example i cut it at the section with the largest opening.



Ignore the 2 black pieces of plastic in the photo, its just some spare bits from part of the cut out section that i figured could be useful to cover gaps. Didn't get to use them eventually.


Step 3:

Measure and nest a length of 13mm SingaPlastics PVC pipe inside a shorter length of 16mm PVC pipe, this will become the connection point.

Open up the replacement shoulder stock and position a 13mm PVC end-cap inside, you'll have to trim and sand down the shoulder stock internals until it fits.




Step 4:

Bolt on the connection point pipes to the RFSG shell, i used 2 countersunk machine screws to secure it to the shell. Note that the shell is in 2 layers, so i bolted it to the inner layer.




Step 5:

Drill and sand out the replacement shoulder stock until it has a rounded opening to accept the connection point pipes, then glue the 13mm PVC end-cap permanently inside the replacement shoulder stock. I also added a ring of foam padding to help cover the gaps between the shoulder stock and casing.

Photo: (Left) Original replacement shoulder stock / (Right) Modded replacement shoulder stock.




Step 6:

Assemble everything back together and connect the new shoulder stock, its complete!



The plastic replica M4 shoulder stock i used is adjustable so it could be extended to different positions. Much more comfortable and steadier when shoulder aiming.



One of the main reasons why i did this mod was also because the Doomsayer was originally too long and it could not fit into any of my carrying cases or bags! I was getting sick of carrying it around in plastic bags with all the barrels sticking out! :)

With the shoulder stock being removable, it can now fit nicely into a large padded case.



Nice! :)

Nerf Stampede "SMG" Conversion!

Minimized Stampede... my "SMG" version! :)



Gaps covered by assorted bits and pieces from chopped out parts (guess which parts the bits came from?).



Retained shoulder stock.



Relocated battery pack. It houses 4 x fully charged 14500-size TrustFire Li-Ion rechargeable batteries (unprotected versions) which output a total of 16.8V.



And this is what i call... the "SpamFire" Combo! :)



Check it out in action!

Nerf Dart Tag Swarmfire - Mod Guide!

This Mod Guide will cover some performance mods for the Nerf Swarmfire.

Mods covered:
- Air Restrictor (AR) Removal
- Plunger Air Release Seal
- Plunger Padding
- O-Ring Replacement
- Voltage Increase
- Aftermarket Spring Replacement
- Rotating Barrel Dart Post Removal (Optional)

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

:: AR Removal ::

Step 1: Disassemble your Swarmfire. Make sure to remove all the screws before detaching the casing layers.




Step 2: Open the motorized spring plunger casing. Move aside the cover, rotating barrel and battery sled.




Step 3: Separate all the spring plunger parts and gear components.




Step 4: Take the plunger tube and simply use flat-head precision screwdrivers to pry open the plunger cap... the AR components will just pop out.



Discard the AR components and glue the plunger cap back on with 2-part epoxy glue.

Alternatively, the AR can also be drilled out with a motorized drill or dremel. Just make sure the plunger and seals are not damaged in the process.

Left Photo: Cap Before AR Removal / Right Photo: Cap After AR Removal.



Left Photo: Tube Before AR Removal / Right Photo: Tube After AR Removal.



Note that the white colored "target" shaped plastic grill has to be intact, that part is required as an impact barrier for the plunger rod.

The AR removal mod is done!


:: Plunger Air Release Seal ::

Close up the air relief hole on the side of the plunger tube. This is essential to create an air-tight plunger seal.

Top Photo: Open / Bottom Photo: Closed.



In my example, i use 2-part epoxy glue to fill in the air relief hole.


:: Plunger Padding ::

Without the AR, there is no air buffering system to cushion the plunger on tube impact.

This results in very high wear and tear on the plunger and tube casing, by both normal firing and dry firing. Due to repeated direct impacts on the tube (hence the loud cracking sound during firing) over time, the plunger and tube may become damaged.

Therefore, padding should be applied to the plunger to help cushion the impact.

In the following photo, i attached a 20mm diameter soft bumper padding to the tip of the plunger.



The 20mm diameter soft bumper pads i used in the above example are from a brand called "Volkmar-Fix", they can be found at most common hardware shops.




:: O-Ring Replacement ::

To test the plunger air seal, block the tube exit and try to push the plunger rod into the plunger casing, if the air seal is optimized, there should be some resistance in the plunger. It should still be able to move smoothly when the tube exit is not blocked.

If the plunger seal is loose, simply replace the stock o-ring with a more air-tight aftermarket o-ring.

From my experience, the plungers in different Swarmfire units can differ slightly in diameter, therefore you may have to test various o-rings to find the ideal ones that fit properly for an air-tight seal.

Photo Left: Stock O-Ring / Photo Right: Aftermarket O-Ring




:: Voltage Increase ::

The voltage feed to the Swarmfire's motor determines its speed.

To increase the Swarmfire's Rate of Fire (RoF), simply increase the amount of voltage to its motor.

There are many different types of batteries available to create higher voltage power sources, its up to the users to determine which setups suit their usage best.

In my examples, i choose to use 14500 size 3.7V Li-Ion Rechargeable Batteries (Brand: TrustFire / Unprotected versions) for my modded Swarmfires.

Such batteries can be installed in the original Swarmfire battery sled without additional modification, simply use AA to C-battery converters.



14500 size 3.7V TrustFire unprotected Li-Ion rechargeable batteries can be charged up to 4.2V each, so i use 4 of them in C-battery converters (with an additional 2 dummy spacers) to get around 16.8V of power.




:: Aftermarket Spring Replacement ::

One way to increase the speed of air delivery through the plunger tube is to replace the stock spring with a stronger aftermarket spring.

Photo Top: Stock Spring / Photo Bottom: 10kg load Spring



Note that due to the thicker spring wire of stronger aftermarket springs, the plunger rod's 4 plastic strut "fins" at the front will need to be trimmed abit narrower so that the spring can fit over the rod properly (or else the spring will end up sitting too far back).

For an optimal balance of RoF, range and reliability, i currently use 10kg load aftermarket springs with 16.8V power on my modded Swarmfires.

Note that i use TrustFire 14500 unprotected Li-Ion rechargeable batteries. These unprotected Li-Ion batteries have high discharge rates which are necessary to provide the required torque to the motor to handle heavier spring loads.

Be advised that regular Alkaline batteries may not have high enough discharge rates (separate factor from voltage) to enable the motor to pull such heavier spring loads.

:: Rotating Barrel Dart Post Removal (Optional) ::

This mod is optional, it is mainly for users who want to be able to use solid core DIY foam darts (ie. stefans) or as a modding step before re-barrel mods.

Detach the rotating barrel from the casing.



Use a dremel with a drill or cutting bit to remove the dart posts.

Note that the dart post removal mod does not affect power or range significantly, it just allows more flexibility in the usage of various DIY foam dart designs.


:: Modified Nerf Swarmfire - Test Fire & Range Testing Video ::




:: Sample Test Fire Data ::

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

Distance is measured at where the shot lands (Average of 20 shots).

Stock Swarmfire
PTG = 20 ft
ATG = 30 ft

Modded Swarmfire (AR Removal & 10kg Load Aftermarket Spring)
PTG = 60 ft
ATG = 75 ft

Note that the tests were done under controlled conditions with Nerf Tagger foam darts. The results are sample estimates for reference (your results may differ depending on materials and mod techniques used).

Nerf Dart Tag Swarmfire - Internals Guide!

This guide will serve as a reference for the internals of the Nerf Dart Tag Swarmfire.

For a detailed review of the Nerf Swarmfire, click Here.

Nerf Dart Tag Swarmfire - Exterior Shell Removal (Layer 1)




Nerf Dart Tag Swarmfire - Exterior Shell Removal (Layer 2)




Nerf Dart Tag Swarmfire - Internal Components




Nerf Dart Tag Swarmfire - Motorized Plunger System




Nerf Dart Tag Swarmfire - Trigger System




Nerf Dart Tag Swarmfire - Direct Spring Plunger




Nerf Dart Tag Swarmfire - Direct Plunger Internals

Nerf Dart Tag Quick 16 - Internals Guide!

This guide will serve as a reference for the internals of the Nerf Dart Tag Quick 16.

For a detailed review of the Nerf Quick 16, click Here.

Nerf Dart Tag Quick 16 - Exterior Shell Removal (Layer 1)




Nerf Dart Tag Quick 16 - Exterior Shell Removal (Layer 2)




Nerf Dart Tag Quick 16 - Exterior Shell Removal (Layer 3)




Nerf Dart Tag Quick 16 - Internal Components




Nerf Dart Tag Quick 16 - Reverse Plunger System

Nerf Dart Tag Speedload 6 - Internals Guide!

This guide will serve as a reference for the internals of the Nerf Dart Tag Speedload 6.

For a detailed review of the Nerf Speedload 6, click Here.

Nerf Dart Tag Speedload 6 - Exterior Shell Removal (Layer 1)




Nerf Dart Tag Speedload 6 - Exterior Shell Removal (Layer 2)




Nerf Dart Tag Speedload 6 - Exterior Shell Removal (Layer 3)




Nerf Dart Tag Speedload 6 - Internal Components




Nerf Dart Tag Speedload 6 - Reverse Plunger System

Nerf Dart Tag Sharp Shot - Internals Guide!

This guide will serve as a reference for the internals of the Nerf Dart Tag Sharp Shot.

For a detailed review of the Nerf Sharp Shot, click Here.

Nerf Dart Tag Sharp Shot - Exterior Shell Removal




Nerf Dart Tag Sharp Shot - Internal Components




Nerf Dart Tag Sharp Shot - Reverse Plunger System