January 16, 2016

Nerf Darts and Rifled Barrels - Part One

The question of rifled Nerf barrels comes up from time to time - since Nerf darts (especially the Elite and Mega darts currently on the market) have issues with erratic flight at medium to long range, there is always the desire to fix these accuracy issues. Since many Nerf barrel attachments have rifled grooves (for cosmetic reasons only, since the faux barrel is too wide to do anything useful), modders have wondered whether grooves in a real barrel would have an effect.


Generally speaking, there hasn't been definitive proof of rifled barrels positively affecting dart flight. The first major authority on the subject would be Ben Trettel, a.k.a. Doom from the NIC. This blog post explains why rifling hasn't been shown to help darts. Basically, darts are generally already stable in flight because they are weighted more toward the front, and the center of pressure sits behind the center of mass. At most, there have been only anecdotes in support of rifled barrels. Quite simply, it's easier to fix the dart's mass and drag issues than it is to achieve spin stabilization.


But what about larger ammo, or homemade ammo? Nerf arrows, Demolisher rockets, and Titan missiles all use spin stabilization. However, these are all very lightweight for the volume they take up. Since an increase in mass would decrease ranges by a significant margin, the extra drag from spin stabilization is an acceptable tradeoff for stable flight. Meanwhile, the foam backer rod used for stefans isn't always straight, especially for the larger sizes. This area will be the focus of my current experiments.
My decision to start experimenting occurred by pure serendipity. When I found the Xshot Max Attack in Canada, I discovered that the fake barrel was virtually identical in inner diameter to 1" Sch40 PVC. In addition, it had rifled grooves, with a left-hand twist (roughly one turn every 19", although the barrel is closer to 12" long). So I adapted it to couple to 1/2" PVC, did the same with the 1" PVC barrel, and used my tried and true Big Blast as the shooting platform.


I made several dozen darts out of 1" FBR, measuring about 2" long and averaging 5.0g in mass. All were numbered and marked.


All dart masses have been recorded, as has other information; the notebook picture is just from the start of my experimenting. I've made more darts since then to try to make more data points in the future.


Finally, we have the first step of the experiment: showing whether or not the stefans are actually turning due to the rifling of the barrel. To that end, I chose ten of my darts at random (pictured further up), and fired them out of both barrels.



If you want to examine the video frame by frame, I recommend this free extension from the chrome web store.

So far, it appears that rifling does induce some spin into these large stefans. Future posts will delve into things like effects on range and accuracy, if there is a practical limit for what size foam this will affect, etc.

EDIT: One viewer asked if I could mark the darts differently for easier viewing. Here you go!

2 comments:

  1. A guy in Singapore made a rifling section for barrels(mainly for rebarreled long shots) that seems to have a positive effect. You can find a video on PsyK's channel about this.

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