WarMachine

1. They are really fun as well as non-threatening and non-destructive.
2. High performance in a lightweight and affordable package. 
3. I would not spend more than $70 on a nerf blaster that complies with the stored energy laws for toys here in the U.S.
4. in order from most to least important: Accuracy, Range, Weight, # of shots per load, size, and finally Aesthetics.
5. I generally prefer darts in the same format as "nerf elite darts". 
6. For the most part I like to use ether a carbine or a rifle.
7. While i prefer semi-auto I generally will not use flywheel based blasters.
8. I would consider myself somewhere between a 4 and a 5 as i am by no means an expert but i do have a considerable amount of experience in this hobby.
9. I would love to see nerf return to air tanks and bladders as air tanks allowed for long range, high power, and accurate shots while air bladders allowed you to get several shots out of an air tank based system.
10. My ideal nerf blaster can not be quickly defined. Ideally I would use a nerf blaster that fires from an expanding pneumatic air tank that uses its expansion to actuate its breach it would be fed from an air bladder as well as a dual action 7 inch stroke pump that would ideally bring you to operating pressure in 1 or 2 strokes.

You will need some way to seal the front of the barrel. Most people use packing tape for that purpose but if you have the time for it i would either find or make a rubber cup that you could put on a cord that would go over the end. Now for the barrel it self i would advise schedule 80 3/4 inch pvc as i have found that to be a nice snug fit for mega darts but be careful with that as not all batches of mega darts will fit. The next thing that should be of note is that the first 4 to 5 inches of the barrel where the dart would sit should be fluted and the point where the vacuum is applied should be between the fluted section and the valve for your high pressure supply with some form of post to stop the dart from covering that point to prevent the negative pressure from destroying the darts. Aside from all those things i would suggest that you run some vacuum test so that you know how low you can take the barrel pressure before it destroys the dart. Also please note that at the point where your dart has reached the front of the barrel you need to be at atmospheric pressure to prevent the dart from rupturing.