If you’ve never dry fired a compound bow before, consider yourself lucky. While I’ve been lucky myself and not accidentally done it, I have been around others who have and it can be nerve wracking, a bit scary, and a total bummer.
Dry Firing a Compound Bow (firing the bow without an arrow in it) can result in damage to the bow and sometimes even catastrophic failure and possible injury to the archer. You should never dry fire a bow and any compound bow that has been dry fired should be thoroughly inspected for damage before further use.
Like a toddler with endless questions you may be asking “but why?”. Because of physics my friend, but let’s take a closer look at what happens if you dry fire a compound bow and why you should NEVER do it.
What Happens When a Compound Bow is Dry Fired?
The short answer – all hell breaks loose. Ok maybe not, but it could. But that answer is too simple and leaves you with more questions. So time to break it down a bit so you can understand the what’s and why’s of a dry fire.
Storing and Transferring Energy
A bow, whether compound or traditional, is a device that stores and transfers energy. When you pull a bow to full draw the stored energy in the limbs of the bow has potential to transfer energy at the point of contact from the string to the arrow.
When you release the string, the bow’s stored energy is transferred into the arrow and becomes kinetic energy.
Kinetic Energy = energy which a body possesses by virtue of being in motion.
It should be noted at this point that the law of conservation of energy states that energy can not be created nor destroyed, only transferred. What this means in terms of archery is that the energy stored in the bow has to go somewhere, it can’t be destroyed so therefore it’s transferred.
The percentage of the bow’s energy that is transferred into the arrow is called the bow’s efficiency and it’s calculated using the following formula.
Bow Efficiency = (Kinetic energy / stored energy) x 100%
I’ll spare you the mathematics of it all, but if you’d like to read a really good explanation of the physics and math of all this visit Archery Historian.
So why is that formula important? Well because the higher the efficiency the more kinetic energy is transferred giving it somewhere to go, because remember we can’t destroy it.
Some of the energy is transferred in other ways, heat for example. The rest of the stored energy is transferred or absorbed back into the bow as vibration. This is perfectly fine and design of the bow takes this into account.
However, we’ve finally reached the point of all this science and math mumbo jumbo. If you remove the arrow from the above equation, you’ve lost the transfer of stored energy into kinetic energy other than the very minor resistance of air and friction of moving parts.
This means all of that stored energy is now absorbed back into the bow. Most modern compound bows can provide 50-100 lbs. of kinetic energy. That’s a lot of force being transferred back into the various parts of your bow, much more than it’s designed to handle.
Does the absorption of energy from a dry fire ruin a compound bow?
A compound bow is more complex than a traditional longbow or recurve. It has moving mechanical parts and pieces to varying degrees depending on how it’s built.
Here are the basic parts of a compound bow:
- Cams and/or Wheels
- Cables and String
When a bow is dry fired and that energy is absorbed back into the bow it will transfer to all of these parts in one way or another. While these parts are designed to absorb some energy over thousands of shots fired, they are not designed to absorb that much energy all at once.
Each part is potentially affected differently and it’s unpredictable. No two bows will react the same to a dry fire. We can make some generalizations however.
Risers are usually either cast or machined and are probably the most durable part of a compound bow. They’re unlikely to be affected by a single dry fire but not impossible.
Check the riser for cracks if the bow has been dry fired. Especially on magnesium risers which are more likely to be an issue.
A compound bow’s limbs are the main source of stored energy, but this doesn’t mean they can take the large hit of transferred energy from a dry fire. It makes no difference if you have solid limbs or split limbs. Both are at risk of damage.
Check for cracking or checking on the limbs. Be diligent and check them thoroughly, a failure here could be very hazardous for your health. In addition to cracks, they need to be inspected for any twisting or other signs of fatigue.
Cams and Wheels
These little sweethearts are what your cables are connected to and partially control your draw length and let off percentage. They are largely what makes a bow a compound bow.
You may have already guessed but these can also be damaged by a dry fire. They can bend and warp or even develop small cracks. These will also need to be inspected well.
The axles are an often overlooked but crucial part of a compound bow. These are what the cams or wheels ride on and allow them to rotate. Not unlike the axles in a car.
In the few dry fires that I’ve witnessed or been privy to, the axles were almost always bent afterwards. These will need to be inspected for sure.
Cables and String
The cables and string of a compound bow are crucial to its function. Luckily, following a dry fire they aren’t that likely to have been damaged.
However, it’s still wise to inspect them for anything obvious such as excessive fraying or broken strands.
What do you do after a dry fire – Is the Bow really Ruined?
In most cases, no the bow isn’t a total loss. Some people get lucky and there’s no damage at all. It’s very unpredictable.
The first thing you should do after a bow is dry fired, is NOT use it. You DO NOT want to be on the receiving end of a catastrophic failure. I’ve heard horror stories of limbs coming loose and hitting the archer. Let’s try to avoid that.
The bow needs to be carefully inspected for signs of damage. Have a reputable shop or bow tech do this unless you are well versed in the repair of compound bows.
You certainly could replace any part of the bow that is damaged as long as it’s available for purchase but it may be cost prohibitive to replace limbs and risers. Springing for new cams and axles however isn’t the end of the world and those are probably the most common issues after a dry fire.
It’s worth noting that shooting an arrow that’s underweight for your bow is also potentially damaging. It may not happen after a single shot, but it will take its toll over time.
Bottom line is NEVER DRY FIRE A BOW. One way to avoid this is ALWAYS nock an arrow before you draw the bow even if you don’t intend to fire it (obviously don’t point it at anyone or anything you don’t want to shoot).