Today's hunting crossbows are lighter, smaller, more portable, and shoot much faster than the models that were sold just 8-10 years ago. Arrow velocities of 420 to 470 are not uncommon. And they usually come equipped with advanced scopes to assist with accuracy.
They look like some kind of exotic sniper rifles. So it's easy for one to subconsciously perceive them as deadly devices for long-range takedowns. But they are not. Modern crossbows, despite all technical advancements, are still close-range weapons.
Let's set this straight away - in a hunting scenario, you should not attempt a shot with a powerful modern crossbow at an animal that is more than 50 yards away. Beyond that distance, the chances to get an ethical kill and to recover it successfully drop dramatically.
I hope you noticed the "powerful modern" part? That roughly means a model that shoots 400-grain or heavier arrows with 400 or more feet per second. If yours is an older or a less capable model, you should pull that max distance closer - to 40 or even 30 yards.
Now, if you are just practicing and want to test the long-range accuracy of your crossbow, you can try increasing the distance to about 100 yards. But in this case, you would have to aim way above the target due to the enormous arrow drop.
Here is an example: a 400-grain arrow with an initial speed of 400 feet per second will drop 93 inches before reaching the 100-yard mark. And yes, you can find scopes on the market like Excalibur Tact-100 that can assist you even at such range.
But hunting with a crossbow involves a considerable deal of responsibility. A couple of inches off and you'd miss the animal's vital organs. And hitting anywhere else would most likely result in a hurt animal that may or may not die hundreds of yards (or even miles) away so you won't be able to recover it.
There is a number of factors that make long-range shooting a risky endeavor:
Despite their impressive initial speed, gravity starts affecting crossbow arrows progressively after they've flown more than 50 yards through the air. For example, a 400-grain arrow with starting velocity of 400 fps would drop 29 inches at the 50th yard and 43 inches at the 60th yard. Use the following table to get a better idea of how much you'd have to compensate at different distances:
|20 yards||30 yards||40 yards||50 yards||60 yards||70 yards|
Note: you can play with the Arrow Ballistics Calculator if you want to get a better idea of the capabilities of past and current crossbow models.
It is clear that the newest and most powerful crossbows have the advantage of flatter trajectory at all distances. And the gap is much more dramatic if we compare them with older or slower models. But even a 450-fps crossbow can't overcome the pull of gravity in a way that makes shooting at live animals past 50 yards ethical or practical.
Let's say you have a 350 fps crossbow and you've learned to hit your targets somewhat reliably at 35 to 40 yards. At this range, the arrow would drop 20"-25".
You've practiced enough and you are comfortable with this loss of height.
Upgrading to a more powerful 450 fps model would allow you to extend that range with around 10 yards because you'd have to calculate the same (or very close) drop.
Partially related to the vertical drop, the angle of entry of the arrow increases progressively after 40-50 yards. That makes it harder to predict the orientation of the wound channel that is created by the arrow broadhead.
An arrow starts losing speed and kinetic energy the moment it leaves the weapon. If we use the same example 400 grain arrow with an initial speed of 400 fps, we'd see that by the time it travels 50 yards through the air, it would lose 8% of its speed, 11% of its kinetic energy and 6% of its momentum.
Losses with lighter arrows are more prominent. Here's a similar comparison table:
|0 yards||20 yards||30 yards||40 yards||50 yards||60 yards|
It is obvious that the values at 40 yards and further are quite different. Less kinetic energy and especially the reduced momentum translate to lower penetration and shallower wound channel.
The trajectory of any projectile can be affected by the wind but that is particularly valid for arrows, because of their large surface area (compared to, say, bullets). This is emphasized even further when using fixed broadheads as they bring extra surface that can catch air.
So a crossbow arrow can be pushed off its course quite a few inches at distances over 50 yards. And a few inches are often enough to miss the vital organs of an animal. For instance, the size of the vitals area of a whitetail deer is 6-7 inches.
Also, keep in mind that wind might be blowing harder 50 yards away from you or where your target is.
The speed at which sound travels through the air is 1125 feet per second. This is more than twice faster than the speed of the fastest crossbows on the market.
In practice, this means that the animal would hear the shot before the arrow reaches it.
Let's say you are equipped with a top crossbow model that shoots with 470 fps. If you are using it to shoot a deer that is 70 yards away, it would take only 0.186 seconds before it hears it, but the arrow would need 0.45 seconds to get there.
And this difference might not seem much but is enough for the nervous system of the animal to process the sound and send its reactionary signal to the muscles.
Naturally, the gap in time between the sound and the arrow arrival gets bigger with distance. So the further away the deer is, the greater the chance it moves away from the arrow path.
Even if aiming through a scope, it is very possible that you miss noticing tiny objects that might be between the arrow and your target. The arrow can glance off of grass, a branch, or a leaf and get diverted from its intended path.
Modern crossbows allow for shooting at longer distances - there is no doubt in that. But not by that much if you compare them to older models like those that were produced 10 years ago. If 35-40 yards was considered a sensible maximum distance for hunting in 2010, today you can add around 10 yards to that. But not more.
Especially if you aim to be a responsible and ethical hunter.