First, let’s take a look at how Maryland wrote their proposed law, HB888. Specifically, I will be citing line 28, page 3.

(J) (1) “RAPID FIRE TRIGGER ACTIVATOR” MEANS ANY DEVICE, PART, OR COMBINATION OF DEVICES OR PARTS THAT IS DESIGNED AND FUNCTIONS TO ACCELERATE THE RATE OF FIRE OF A FIREARM BEYOND THE STANDARD RATE OF FIRE FOR FIREARMS THAT ARE NOT EQUIPPED WITH THAT DEVICE, PART, OR, COMBINATION OF DEVICES OR PARTS.

Never mind that they might as well have called it “Shooty Thing That Makes Guns Shoot Faster”. This law doesn’t do what you think it does. What does “rate of fire of a firearm” mean? And what devices or parts could affect that?

Before we discuss bumpstocks, we need to understand a far more fundamental principle. What is the “rate” of something? Most often, we use it to describe the frequency that something happens. And now I’m getting excited, because this is a math term. I get math. (Mostly.) Let’s look at some examples of rate.

Rate of travel is pretty easy to understand. Speed is the measure of how much time it takes to drive a certain distance. The higher your speed, the more distance you can travel in the same period of time. Obviously there are different systems for measuring distance and time — but miles and hours are commonly understood units, and provide comfortably sized whole numbers, like 55 MPH.

In order to measure rates like speed, you need to look at a window of time. If your morning commute is 15 miles, and it takes you 20 minutes, you could say your speed was 45 MPH — although most people would say this is more representative of your average speed. Police officers are much more interested in how fast you’re driving “this instant”. Mathematically speaking, this is slightly impossible. If the window of time is “zero seconds” (truly instantaneous)… it’s complicated. You’re dividing by zero. Bad things happen in math when you divide by zero.

However, all is not lost. If I can measure the distance you travel in the time it takes to blink an eye, that’s close enough to “instantaneous” for me. (This is effectively the fundamental theorem of calculus, by the way.) The way police officers do this is with a LIDAR gun.

Simply put, LIDAR measures the distance to an object by firing a beam of light and measuring the time it takes to strike the object and reflect back. Note that this is only distance! In order to measure speed, the gun does this again and again over very short periods of time — far less time than it takes to blink an eye. If you travel 30 feet in the blink of an eye, your speed is 60 MPH.

(For further reading, you may be interested in the solution to Zeno’s Paradox of Motion… but I’m already in too deep.)

Concerning guns, there’s a seemingly insignificant, yet interesting change. Travel is a continuous process, but firing a bullet is a discrete process. That is to say, I can drive half a mile, but I can’t fire half a bullet. For a discrete process, rate is the amount of time for a cyclic event to complete and start again. If the event does not start again, it doesn’t make sense to talk about rate.

Consider a stapler. The process begins when you press the plunger: one staple is applied to the stack of papers. The process ends when you release the plunger. It is not cyclic. You can wait an infinite amount of time for another staple, but it will never come. You can’t measure the time between staples, because there is only one staple. A stapler does not have a rate of fire.

Now certainly, I can mash the stapler as fast as I want— but there’s a significant difference here. We’re talking about how fast I can staple, not how fast the stapler can staple. If I fashion the stapler in the shape of a hammer and duct tape two back to back, I might be able to staple twice as fast, but I’d also look like an idiot, and get nothing done.