This Mod Guide will cover some performance mods for the Nerf Stampede.
- Air Restrictor (AR) Removal
- Plunger Rod Air Release Seal
- Plunger Padding
- O-Ring Replacement
- Voltage Increase
- Aftermarket Spring Replacement
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 Stampede. Make sure to remove all the screws before detaching the casing.
Step 2: Disassemble the plunger mechanism components and remove the plunger rod from the plunger casing.
Step 3: Use long screwdrivers and a hammer, carefully knock out the Air Restrictor (AR) assembly from both ends of the plunger and bolt.
Left Photo: Stock Air Restrictor / Right Photo: Air Restrictor Removed.
:: Plunger Rod Air Release Seal ::
Look at the front and back of the plunger tip, notice the 2 air release holes?
For a better air seal, use super glue or epoxy glue to seal both of them.
:: Plunger Padding ::
Without the AR, there is no air buffering system to cushion the plunger on bolt impact.
This results in very high wear and tear on the plunger and bolt casing, by both normal firing and dry firing. Due to repeated direct impacts on the bolt (hence the loud cracking sound during firing) over time, the bolt and plunger 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 bolt 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 bolt 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 Stampede units can differ slightly in diameter, therefore you will have to test various o-rings to find the ideal ones that fit properly for an air-tight seal.
Photo Left: Aftermarket O-Ring / Photo Right: Stock O-Ring
:: Voltage Increase ::
The voltage feed to the Stampede's motor determines its speed and torque.
To increase the Stampede's Rate of Fire (RoF), simply increase the amount of voltage to its motor.
In my examples, i choose to use 14500 size 3.7V Li-Ion Rechargeable Batteries (Brand: TrustFire / Unprotected versions) for all modded Stampedes.
I prefer to use these type of battery sizes due to their versatility in usage. Because of their AA compatible size, they can fit into multi-slot AA battery holders, and are not just limited to specific hobby or modding usage, they can also be used other devices like CREE torch lights or even to replace normal batteries in compact electronics devices (with proper voltage matching).
Such batteries can be installed in the original Stampede battery sled without additional modification, simply use AA or 2AA to D-battery converters, or use multi-slot AA battery holders.
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 a 4AA battery holder to get around 16.8V of power.
Notice how little space these rechargeable batteries require. :)
These 14500 size Li-Ion rechargeable batteries are compact and lightweight. Although their 900mAh capacity are low compared to other batteries, i've tested sets at full charge and have managed to fire around 40 x 18-dart clips worth of foam darts before the battery sets require recharging.
That's more than 700+ shots per charge, more than enough for most Nerf games.
As a reserve, i usually just carry an extra spare set for extended Nerf games or when the first set is recharging.
:: Aftermarket Spring Replacement ::
One way to increase the speed of air delivery through the bolt is to replace the stock spring with a stronger aftermarket spring.
There are many different springs with different sizes and spring force ratings. Spring choice will depend on your usage.
The examples below show the stock spring compared with 3 other aftermarket springs.
Photo (Left-Right): Stock Spring, 6kg load Spring, 9kg load Spring, 13kg load Spring.
Tested effects and usage of the various aftermarket springs shown above:
6kg load Spring- Works with 9V but RoF will be reduced by 50%, recommend >12V for better RoF.
9kg load Spring- 9V has difficulty moving the plunger, 12V gets normal RoF, recommend >15V for better RoF.
13kg load Spring
- 12V has difficulty moving the plunger, 15V gets normal RoF, recommend >18V for better RoF.
Note that the above voltages are tested with 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 protected versions or regular Alkaline batteries may not have high enough discharge rates (separate factor from voltage) to enable the motor to pull such heavier spring loads.
For an optimal balance of RoF, range and reliability, i currently use 9kg load aftermarket springs with 16.8V power on my modded Stampedes.
Photo Top: Stock Spring / Photo Bottom: 9kg load Spring
:: Modified Nerf Stampede - Test Fire & Range Testing Video ::
All the above modifications will result in this...
:: 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 dart lands (Average of 6 darts).
PTG = 20 ft
ATG = 30 ft
Modded Stampede (AR Removal & 6kg Load Aftermarket Spring)
PTG = 45 ft
ATG = 60 ft
Modded Stampede (AR Removal & 9kg Load Aftermarket Spring)
PTG = 60 ft
ATG = 75 ft
Modded Stampede (AR Removal & 13kg Load Aftermarket Spring)
PTG = 70 ft
ATG = 85 ft
Note that the tests were done under controlled conditions with customized foam darts. The results are sample estimates for reference (your results may differ depending on materials and mod techniques used).