The Truth Behind Compound Bow Speed Ratings

Compound bow speed ratings are all the rage, but do you know the true ins and outs of the standards?

The Truth Behind Compound Bow Speed Ratings

Whether it’s an ego thing or otherwise, numerous bowhunters think speed will alleviate their problems. It’s been that way for a long time. In 2002 when I first started working at my family’s archery pro shop — a 320-fps bow was considered screaming fast — many guys were hellbent on having the fastest bow possible. To them, it was all about reaching a certain number. If they didn’t, they were unhappy.

Today, little has changed, and many bowhunters still don’t quite understand the complexity behind bow speeds. They see a number listed in a catalog or on a website, and think they’ll achieve it if they buy that bow. However, it rarely happens. Let’s look at a few reasons why.

 

How IBO/ATA Bow Speeds are Calculated

I can understand why some folks become upset when a bow listed at 350 fps shoots far slower when set up and adjusted to their specs. For that reason, it’s imperative to know how manufacturers obtain IBO/ATA speeds.

Manufacturers essentially maximize the rating when calculating IBO/ATA speed by using metrics that are usually unrealistic for most folks and bowhunting applications. For the ATA standard, the draw length is set to 30 inches. Few bowhunters fit into a 30-inch draw length. Next, the bow’s draw weight is set to 70 pounds. Although many can, most bowhunters cannot or shouldn’t draw 70 pounds. Next, a lightweight arrow of 350 grains (arrow plus field point) is used for testing. That’s the bare minimum arrow weight before you risk damaging the bow, and most bowhunters shouldn’t shoot such a light arrow, especially if hunting big game. Lastly, the bowstring is bare — no peep sight or silencers to slow down the bowstring.

The IBO standard is similar, measured with a 30-inch draw length and an arrow weighing 5 grains per pound of draw weight; otherwise, exactly equivalent to ATA at 30 inches of draw and 70 pounds of draw weight (350-grain arrow).

 

Actual Velocity

So, what velocity can you expect to achieve if you purchase a bow listed at 340 fps? Well, let’s suppose you shoot a 29-inch draw length. That alone will usually reduce the speed to 325 to 330 fps. Add two string silencers and peep sight, and you can expect to be down to 315 to 320 fps. Set your bow to 60 pounds instead of 70, and you’ll likely land in the 300 to 310 fps. Of course, shooting a 400-grain arrow will reduce your speed well below 300 fps, likely in the 280- to 290-fps range. Of course, these are all estimates, but are indicative of the reality you don’t see when your eyes see a 340-fps listed speed.

 

Bridging the Gap Between IBO/ATA and Actual Velocities

Now that you understand how bow and arrow specs create actual velocity, this question might be burning a hole in your mind: Can I achieve 300 fps or greater with non-IBO/ATA specs?

Using the example bow we discussed in the last paragraph, the answer is yes. You could shoot a 360-grain arrow, tweak the poundage up to 62 pounds and eliminate bowstring silencers. The question is, are the additional feet per second you’ll attain by making those substitutions worth it?

I’ll argue they aren’t. Wringing out every available foot per second your bow can muster usually solves nothing, and in some cases, it can be detrimental to your bow’s overall performance. We’ll discuss why next.

 

Speed Generally Means Sacrifices

Milking out every foot per second might seem logical, especially because “speed kills” has become an accepted phrase in the bowhunting world. However, it’s hardly a wise choice. Why? Because you sacrifice one thing for another.

One example is shooting an ultralight arrow. Yes, your velocity will increase, but a soda-straw arrow creates other dilemmas. First, you’ll experience greater wind drift, especially when shooting at longer distances. Second, an ultralight arrow, particularly when front-of-center isn’t correct, will penetrate poorly on game. I saw this happen years ago when a hunting partner struck a gobbler’s wing butt using a 70-pound bow with a light arrow with poor FOC. The arrow virtually bounced off after breaking the wing. Fortunately, the bird was recovered, but follow up was necessary.

Further, a lightweight arrow loses energy faster as it travels downrange. A heavier arrow creates a lot more forward momentum. Consider this analogy. An economy car requires less stopping distance than a pickup truck, and that’s because the truck’s additional weight creates greater energy or momentum after it gets moving. See what I mean?

In general, if you’re going purely for the highest speed number you can achieve, you’ll usually experience other problems on the back end, because you’ll almost always sacrifice one thing for another. So, ask yourself: Is speed more important than overall kinetic energy? I’ll always argue that it is not. Sure, speed can deliver a fast arrow, but it cannot make an ultralight arrow penetrate deeply, especially when thick hides and robust ribs are on the receiving end.

 

Speed by Application

In the past, I’ve shot numerous speed bows and numerous more forgiving bows. Regardless, I don’t veer from my 400 grain or heavier arrows (arrow plus broadhead) because I know they’ll penetrate well. I could hit 300 fps if I wanted to, but numbers are unimportant to me. I want a bow that delivers a deep-penetrating arrow/broadhead combo. Period.

Now, I can’t entirely ignore the merits of faster velocity. A quick arrow produces a flatter trajectory. For the archer shooting a multiple fixed-pin sight, gaps between pins will tighten with a speed bow. In turn, this takes some guesswork out of yardage estimation if an animal should take a few steps after you’ve ranged it.

As far as application, energy is less critical for certain game species. Take pronghorn, for example. They are thin-skinned critters and their bones aren’t nearly as heavy and thick as those of deer or elk. For that reason, a lightning-fast bow with lighter arrows could certainly perform okay on pronghorn, but I’ll still opt for my deer rig when chasing even thin-skinned prairie goats. Should my arrow encounter a shoulder blade, it will drive deep enough to collapse the lungs. That creates peace of mind.

Speed bows matched with lightweight arrows are an okay match for thin-skinned animals such as pronghorn, but in the author’s opinion they aren’t the best choice for whitetails and larger game.
Speed bows matched with lightweight arrows are an okay match for thin-skinned animals such as pronghorn, but in the author’s opinion they aren’t the best choice for whitetails and larger game.

Final Thoughts

If someone asks my opinion on speed bows, I don’t steer them away from them. I caution that the brace heights are obviously shorter, and I explain the potential problems that can present. However, I think today’s compounds are so shootable that even a speed bow with a short brace height will usually perform well for most solid shooters.

On the other hand, it’s when someone tries to milk out feet per second by making ill-advised substitutions that I think they’ll experience problems. I believe you’re better off finding middle ground. For me, that’s a bow with a relatively fast IBO/ATA rating and paired with a 420-grain arrow/broadhead and outfitted with bowstring silencers. I get a quiet, somewhat-fast bow that can drive an arrow deep. I couldn’t ask for anything more.

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