Barrel and Grenade Cap

The barrel length is a matter of personal preference and material limitations. You must have enough length for the rocket and grenade plus 1/2 inch. Within reason barrel length isn't a big factor though a longer barrel provides more room for air expansion and may affect velocity. The closer the rocket fins are to the grenade the more likely you will need a sabot to protect the rocket fins. Once you have chosen a length, bevel the front, inside edge of the barrel to ease loading. Next, increase the inside diameter of the grenade end until the grenade can slide into the barrel end. Since the grenade won't be removed often, openings for easy removal like the pod launcher are optional. With the grenade in place attach a PVC end cap over the opening. Mark the end cap location on the barrel and remove the grenade before drilling holes through the cap and barrel for setscrews to secure the end cap. The setscrews should be long enough to hold the end cap in place and lock the grenade in place when installed. Now use epoxy to glue the coupler on the end of the barrel, this will create a slightly larger barrel diameter for the Nerf football.

Firing Mechanism

Clearly this is the most challenging part of the design. Many of the pictures show my first failed attempt but you get the idea. The trigger is a metal ruler, obviously there are plenty of substitutes but it proved to be an easy metal to work with. The return spring turned out to be unnecessary and is no longer in my final design. The firing pin is made from a wooden dowel rod though I recommend a stronger material if available. The trigger frame was left over from my Pro-Carbine sniper mod. You can find a variety of trigger frames available on eBay or other online retailers that could work.

The real challenge I found was getting the right angle on the trigger to allow for firing without locking the trigger or requiring an extreme amount of force. The grenade does require a certain amount of force to depress the firing disk and the angles can add to the required tension. All I can say is test, test, and test until you get it right. You won't be able to fully test the trigger until you're nearly complete so be prepare to have a few failed attempts.

The trigger assembly in the final pictures was my second attempt. I used the same design but I had to adjust the angel of the trigger and doubled up on the ruler to give the trigger more girth. Even after these modifications the trigger is extremely difficult to pull. As long as I can get a shot off when it counts; that's all I care about.

I can provide a few additional pointers. The firing mechanism is an extension of the pop launcher design. A smaller end cap and piece of wire clothes hanger are used to hold the firing pin in place. The grenade will provide the return tension on the trigger. The air fittings have been staged to the right side of the internals to make room for the trigger mechanisms. Finally, this is only one way to trip the trigger on the grenade...don't limit yourself to my design if you have a better idea.

Mod Images