Mattel Ultimator with enhanced inner workings.

This is the Mattel Ultimator, circa 1994. It features a rather large and space wasting extension spring as a power source. To me, that just seemed silly, as far as critiques for a foam missile launcher can be silly that is. So like any modder aficionado, I sought to make it better, and documented the build log so others could follow my steps.

To begin, naturally, find yourself a Mattel Ultimator and dive in.

Mattel Ultimator unmodified

Now open it up, take extreme note of all the small pieces, and marvel at how ingenius its design truly is.

Step 2. Take the barrel and spring and put them aside

Step 3. Order a 1’ section of 2.5” ID 2.75” OD Polycarbonate tubing, a pack of K14 springs, and a 2” to 1/2” PVC reducing bushing from McmasterCarr

Step 4. Slap a large metal washer in front of the priming-mech to protect the plastic (Ignore the k26 spring)

Then go ahead and slide on a cut down K14 spring and bolt the plunger head back on

Step 5. Machining the Plunger tube. This is where it gets tricky and people have asked me to do it for them.

First, cut a slot on the top and bottom of the plunger tube, using the stock one as a guide. I did this using my Band-saw.

The slots were 1.25” wide, on both sides, and went down about 1.75” Then you will need to line up the plunger tube for the 2 holes on each side that secure the plunger tube to the gun

And drill them out with a 3/8” drill bit

I screwed this part up a bit and had to widen the holes.

Step 6. Assemble the gun. Tape the bushing, bolt it in, liberally apply some amazing goop to keep the air loss to a minimum, and slap a hopper clip on it.

You know have a Mattel Ultimator that is much more optimized for firing the traditional homemade nerf darts. The dead space of the large orange barrel is now a thing of the past! Congratulate yourself and go play with your cool new toy.

Alternatively, however, you can keep the stock spring, and just use the clear plunger tube for a striking visual effect

For those of you that are curious, this is how the Ultimator catch system works:

It’s essentially a large caulking gun made with parts from Ace.

Issues with this mod:

The Ultimator was able to send a dart 115’ in about 8-10 pumps of the cocking mechanism, however I came across the issue of the plunger rod gradually slipping forward. I’m sure this is a result of lubricant from the plunger coming into contact with the friction based catch mechanism, if this happens to you too, it should dry out eventually to solve the problem.

Mcmaster-Carr #s:
Plunger tube- 8585K341 1 Ft.
Polycarbonate Round Tube, 2-3/4″ Od, 2-1/2″ Id, 1′ Length
Clear Plunger Tube Bushing- 4880K172 1 Each Std-wall (schedule 40) White Pvc Pipe Fitting, 2″ X 1/2″, Hex Bushing, Pipe End Male X Socket F
K14 Springs- 9637K14 1 Pack Continuous-length Compression Spring, Spring-tempered Stl, 11″ L, 1.093″ Od, .105″ Wire

Thanks for reading as always, feel free to post comments, questions, or concerns.

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