1) Rifling the barrel. Probably not possible with Nerf.
2) Adding stabilizer fins to the darts. While this one is theoretically possible with homemades (and frankly, I think it'd be kinda cool), it'd probably be prohibitively work-intensive to make proper fins.
I'm new at making Stefans, so mine absolutely, hands-down suck. I musta got some bad FBR, too, because the hot glue alone is melting it...
Anyways, all my crappy stefans are between 2 and 7/8 inches long and 3 inches long. Depending on how much the hot glue melted the tip down.
I loaded them into an unmodified clip, and fired them from my modded longshot. The modding was simple; remove air restrictors and peg, and I added a moderately weak spring.
They make it about 30-35'. I use a single size "B" fishing weight, but it's one of those annoying removable ones so it has little flanges so it can be taken off the fishing line. Don't know if that affects it.
The stock darts make it over 50', I'd estimate about 55, maybe 60 feet judging by how they bounce off the door at the end of the hall. However, as other people have mentioned, the stock darts have lousy accuracy.
All shots were made flat, with the front gun attached.
Reporting from South-Central PA. The Magstrike can be acquired from the Toys 'r' us in York (albeit at $35), while both the Magstrike and Longshot can be purchased at the Hunt Valley Wal-Mart in Maryland.
Many of the other Wal-Marts I called said that they were re-doing inventory next week, and that they'd probably come in at that time.
I hope this helps some people get the blasters they need.