Before we start, yes it based heavily on the sentinel. No, I have not yet designed the stock.
It's thanksgiving in America today, which means a week off school to do whatever I want. of course, I've used this week to Cad out the mechanism for a Nerf Rifle I desire to build eventually.
The basic idea is a combination of two Ideas I've had in the past. The first was to create a lever action that primed on the pull stroke, making use of the more powerful arm motion, allowing a stiffer prime and Ideally less pain. The second idea was originally to have a rifle that could be primed once, then fired multiple times before re-priming.
The second idea was abandoned, as a trigger mechanism eluded me, and I realized that unless it was a hopper-feed blaster, you'd either have to reload manually or re-prime to chamber another dart. So I decided to keep the dual cylinders, and connect the plungers, allowing for a shorter travel to have twice the effective spring power.
A week of Solidworks later, this was born. (forgive the low quality, solidworks does not export to PNG or JPEG well.) The whole assembly is attached to the post, and an online view can be found here (until the 22nd of December 2018).
I have yet to model a stock, handle, foregrip, outer casing/protective guard, or magazine well, as I was mostly concerned with function-necessary parts. (I will admit to making these parts slightly prettier than strictly necessary when I designed them.)
The design uses a variation of a Rainbow Catch to hold the two plungers. The Breech is actuated by the handle, first moving back to allow a new dart to advance in the magazine, at the same time meeting the plunger catch. Pulling back on the lever chambers the next dart and draws the plungers back, priming the blaster. The trigger then releases the catch as usual, flinging foam downrange at (ideally) high velocity.
At the rear, there is a U-turn Wye pipe. I don't know if any of these already exist, but one can by made by taking two U-bends, cutting them at an angle (30 degrees in this design) and gluing the cut faces together.
I welcome criticism below, as long as there's some usefulness to it, rather than simply berating design choices.
also, First post. Hi!