Nerf by Numbers: How We Chronograph & Test Blaster Performance

Whether you’re a competitive blaster tag enthusiast or a stock-class backyard plinker, comparing blasters and mod parts with each other can sometimes be a little like comparing apples and oranges; it’s one of several reasons the nerf hobby has rallied around a standard set of performance statistics. Still, many variables can alter or skew those numbers, making practical comparisons difficult without a repeatable testing procedure. So, in the interest of transparency, we decided it was about time we outlined how we chronograph and measure blaster and mod performance at our shop. While we’re at it, we’ll tell you the things you need to know to test your blaster’s performance before the big game. Grab a notebook and a calculator because some math and statistics are involved!

 

Terminology

Before we talk about our methodology, we need to talk about vocabulary (Side note: if you haven’t yet, take a look at our nerf hobby glossary page to get a head start). The main statistics most of the hobby tests for are range, velocity, accuracy, and rate of fire. At least in North America, these are measured in US Customary or “Imperial” units: Feet, Feet per Second (FPS), Inches, and Darts per Second (DPS), respectively.

While we love metric units here at Out of Darts for their easy decimal conversions (many of our products and hardware kits come with metric hardware), these performance metrics are meant to be standardized and practical to the hobby, and a majority of our customers reside in the United States. So, we keep with these units for that reason. However, if you live outside North America and want to translate to different units, 1 foot is equal to .3048 Meters. To convert ft/second to meters/second, simply multiply by .3048. There are also plenty of conversion calculators online – including one built into the Google search engine.

 

Muzzle Velocity

The primary unit we measure is muzzle velocity in Feet per Second (FPS). This is the speed that foam ammo is going the moment it leaves the barrel. While some in the hobby naturally chase a larger number for the sake of it, a more practical use of FPS is for planning around or enforcing an FPS cap. For safety and game balance, many clubs and games require blasters to hit below a certain number. Recording FPS allows organizers to place limits on blaster performance fairly and uniformly. It also allows attendees to be better prepared. For instance, the games here in the Pacific Northwest commonly have a 150 cap, so Luke and I plan ahead by choosing blasters (or tuning and swapping springs and spacers) to meet -- and not exceed -- 150 FPS.

If you’ve taken a high school physics class, you will be familiar with measuring velocity and its correlation to force with a few calculations on pen and paper. I still remember the “magic triangle” mnemonic, where you put your thumb over what you want to measure to determine how to calculate it; in this case, we’re looking for velocity, which is = distance / time. But these days, we have the technology which can save us from a headache!

 

What is a Chronograph?

Also known in the hobby as a “chrono” or “chrony,” a chronograph (chrono- = time; -graph = to record) is a calibrated electronic device that calculates muzzle velocity. It uses two light sensors that are a fixed distance apart. By shooting a projectile -- like a foam dart -- through the chronograph, it can time how long it takes a dart to pass each sensor. Since a device can’t blink or misread a ruler, it can record an extremely accurate read on high-speed projectiles.

 

How to Chronograph a Blaster

Using a nerf chrono is pretty simple. Depending on the complexity, you can just turn it on, fire a dart through it, and it should give you some numbers on a screen. Some newer models of chronographs have an app you can connect via Bluetooth, which makes it easier to record averages and other measurements -- including the rate of fire. If your chronograph doesn’t have an app, you can either write down the readings or record a video to refer to later. But keep those numbers handy because they will be important later!

Of course, this blog post is not a replacement for reading the manual of whichever chronograph you use. There's a wide variety of them out there, all of which have different buttons and settings. Make yourself familiar with your model of chronograph and use this article for everything else.

 

Strength in Numbers: Determining Average Performance

However, one shot over the chronograph isn’t enough to accurately understand a blaster’s performance. It’s essential to get an average over multiple repeatable data points when gathering data. In the wise words of Adam Savage:

Depending on the club or event you attend, you will need to record a set of shots with the chronograph before the blaster being measured is allowed to be used. For efficiency’s sake, the volunteers and staff at Endwar 2022 asked each player to shoot five times over a chronograph. With a soft cap of 130 FPS, a five-shot average allowed for one stray dart going above 130 without having to retune or replace that blaster. Similarly, when it comes to publishing blaster performance on our videos and the listings on our website, we have found that 20 shots are the minimum number of data points needed to get a reliable average and know the standard deviation (σ or SD) of that average.

For anyone that needs a refresher in statistics, the standard deviation is a calculation to determine how spread-out data points are away from the mean (average). Recording standard deviation is important when comparing two blasters with the same FPS average; if the variation between shots is wider for one and not the other, you can decide which one is better to purchase. At the minimum, you’ll know that over 2/3 of shots with that blaster or mod part will be within 1 SD above or below our published average.

 

Eliminating Variables

As a part of our 20-shot average, we try to control or mitigate the effects of variables in our testing to isolate a blaster’s performance. Many factors can influence the performance of a blaster, including dart fit, battery drain, humidity, and temperature, just to name a few.

We record our averages with the best and freshest darts we have. For the three most common ammo types, we use Worker gen3+ "HE" standard-weight short darts, Worker Full-Length Darts, and Genuine Nerf Rival "High-Impact" Rounds. Not only are these makes and models of ammo types highly recommended for regular use, but consistently keeping with these darts and balls eliminates one more variable that could affect the FPS average (PS: Check out guest contributor, FoamShepherd's blog post for a more in-depth ammo guide).

While some in the hobby swear by using chronographs outdoors for more even lighting and accurate reads, the Pacific Northwest is notorious for unpredictable weather. To keep other variables controlled – like temperature and humidity- we chose to get a Caldwell G2 Portable chronograph with a dedicated LED lighting kit and shroud so we can keep it indoors and eliminate any other types of lighting that could affect the reading.

As a bonus, this is one of the larger portable chronographs that folds down when not in use. Unlike other travel-sized offerings, this gives us a wide opening to aim down, making it easier to record FPS with blasters that have a faux barrel or ambiguous sight line.

 

How to Calculate Rate of Fire

The second unit we sometimes publish is the rate of fire (RoF), which is measured in Darts per Second (DPS) or sometimes Rounds per Second (RPS). This is how many darts or balls can be fired in a given length of time. This unit is mainly used to compare electronic blasters. As faster and smarter flywheelers and AEBs increasingly come onto the market, RoF is a metric that is slowly becoming more valuable to publish.

When testing the rate of fire, we usually set up a camera. Admittedly, while the chronograph advertises this feature with its mobile app, it sometimes crashes when it receives too many inputs at once and invalidates the reading. If this happens, we’ll film the blaster emptying a full 29-round Tachi mag, put it into our video editor of choice, and count the peaks in the audio waveform. Any weird hiccough or ambiguous shot can be confirmed with the video, but then we can extrapolate an average dart per second reading.

 

The Ever-Elusive Statistic

Accuracy has always been a “white whale” for hobbyists. Ideally, we could test the improved accuracy of porting or SCAR barrels by locking a blaster down and firing at a target but making such a test repeatable has been a challenge. In the case of Accu-Rival vs standard Rival rounds, they seemed to produce marginally better results, but there was a lot of human error in that test because we don’t have a procedure… yet.

And that’s it! This is our procedure for measuring blaster and mod part performance. We aren't perfect; no one is. All we can do is try to do the best we can in publishing accurate results that can be adapted to real-world performance. Hopefully, now you can understand what our numbers mean and perhaps can replicate a version of our system for yourself. - J Perry Heun