What Is The Let-Off On A Compound Bow?: All You Need To Know

by | Mar 19, 2023

Compound bows are known to be extremely powerful and efficient, but they are also very different from single-string bows, like the recurve bow.

One important feature that enables the compound archer to use much higher draw weights with high levels of accuracy is the let-off.

The let-off on a compound bow is the percentage of draw weight that is reduced at full draw. For example, if the draw weight of the bow at full draw is 70lb and the let-off is 85%, then the archer will be holding 10.5lb at full draw.

Compound bows employ a cam and pully system that enables the bow’s shorter limbs to store energy.

In this article, we’ll be looking at how the compound bow uses the cams and pullies to allow the draw weight to be drastically reduced and what that means for the archer.

What Is The Let -Off On A Compound Bow?

The let-off on a compound bow is calculated as a percentage of the bow’s draw weight that is reduced as the bow reaches full draw.

An archer pulling a 70lb bow with an 80% let-off would only have to hold 14lb at full draw, while a 60lb bow with a 70% let-off would be 18lb at full draw.

70% of the bow’s draw weight has been ‘let-off’, or let go just before the string reaches full draw.

Percentages of bow let-off vary depending on the purpose of the archer.

Hunters, who may need to remain motionless for long periods of time in the full draw position prefer to have around a 75-85% let-off because it’s much easier to hold the lighter draw weight for longer periods.

Target shooters, on the other hand, feel that a lower let-off of around 60-75% benefits them more because they get more stability with a slightly higher holding weight at full draw.

How Does Let-Off Work On A Compound Bow?

The let-off on a compound bow is generated by two elements: the elliptical shape of the cams, and the bow’s limbs.

The cams give the bow a mechanical advantage because they can pull more string which means that as the bow limbs are pulled closer to the archer, the potential energy increases.

The cams are calculating how much string is to be pulled before the string hits what’s known as the ‘back wall’. This is the point where the bow has reached full draw.

Check out the graph below to see how where the let-off occurs during the shot cycle.

At a point just before the archer reaches full draw, the cams will turn over faster, transferring the weight of the bow onto the limbs and away from the archer. This is the let-off point.

The archer will feel the weight of the bow dramatically decrease, so as he pulls to full draw and holds, the weight of the bow will be a fraction of its full draw weight.

Can You Adjust The Let-Off On A Compound Bow?

Most bows come out of the factory already set to the highest let-off, but if you want to hold less weight at full draw, there are 2 ways that you can go about it.

  1. Adjusting the draw stop
  2. Changing the cams

Each notch on the draw stop will add or subtract 5% to the holding weight. Using a torch wrench you can loosen the screws on the draw stop and slide the bracket along until you reach the next notch down.

When changing the let-off with this method, you need to pay attention to the draw length, because you will need to adjust it slightly to increase the let-off and get further into the valley.

Make sure to do exactly the same adjustments to both cams to balance the bow correctly.

For the second method of switching out the cams, the draw length will stay the same.

Will Adjusting The Let-Off On A Compound Bow Affect Arrow Speed?

The rate of speed change will depend on which method of adjustment you choose to go with.

If you choose the method of adjusting the draw stop to adjust the let-off, then yes, the speed of your arrows will increase. For example, if you went from a 65% let-off to 80%, then to get there you would have needed to increase the draw length. More draw length equals more speed.

If you switched out the cams to adjust the let-off, then the 65% is faster than the 80%. The draw weight stays the same, but the draw weight won’t be as low. A higher draw weight equals more speed.

Having said that, the speed change in both cases is going to be small.

How To Choose The Let-Off On A Compound Bow

When talking about deciding on a high or low let-off, your purpose with compound archery will determine what you choose.

If you’re a target archer then you will most likely opt for a lower let-off and a higher holding weight. A let-off of around 65% is generally preferred as it gives more stability and control when holding at anchor. With a lower holding weight, the archer will feel less back tension and won’t be able to have as much control over the shot.

If you’re a hunter, then a higher let-off of around 75-85% and a lower holding weight is going to be ideal for your setup.

Hunters need to be able to hold at full draw for long periods of time as any sudden movement when drawing their bow could potentially scare off the potential prey animal.

Like anything, there are pros and cons to both high and low let-off. Let’s look at each one to give a clearer understanding when it comes to selecting what would be better suited to you.

High Let-Off

Pros

  • Makes holding at full draw much easier – This is ideal for bow hunters who need to remain motionless with zero distractions for long periods of time.
  • Less fatigue – The less weight you need to pull and hold means the shoulders and upper back muscles won’t need to work so hard. This means the archer can shoot for much longer.

Cons

  • Poor technique – Archery is all about form, but with less weight to hold at full draw, you won’t be able to feel any tension in the upper back. In order for proper back tension to occur, there needs to be some weight to activate those muscles. Without it, it can lead to a breakdown in proper expansion and follow-through.
  • Less accuracy – With less weight on the draw, you will be more susceptible to instability. Without the weight to pull against through engaging the right muscles, it’s much easier for the bow arm to wander, therefore more difficult to keep a consistent anchor point.

Low Let-Off

Pros

  • More Stability – More weight at full draw means that the archer will have much more control over the shot.
  • Proper Back Tension – Back tension in archery is when the archer fully engages the muscles of the upper back to hold the weight of the bow. This ties in with greater stability and proper form.

Cons

  • Less Holding Time – More weight on the bow means the archer won’t be able to hold at full draw for any length of time.
  • More Fatigue – When engaging proper back tension, fatigue in the muscles will occur much faster, leading to shorter durations on the range.

Does Let-Off On A Compound Bow Affect Accuracy?

In general, compound bow let-off can affect accuracy due to the amount of stability, or lack of stability that the weight at full draw can impose on the archer.

This is why target archers prefer to have lower let-offs of around 65%. If they’re shooting with a 70lb bow, then they will be holding 21 lbs at full draw.

21 lbs is still very light for an experienced archer, but it will still be enough weight to allow the archer to generate back tension, stability and therefore, more accuracy at greater distances.

Hunters, on the other hand, who prefer higher let-offs are more likely to be shooting at shorter distances. They also don’t need to worry about grouping arrows together as there is going to be a larger margin of error.

Conclusion

Compound let-off comes down to personal preference and your purpose in archery. I would suggest that you experiment with your chosen path as to what works best for you.

Of course, there’s no reason why you can’t do both target archery and change to a hunting set-up when it suits you!

2 Comments

  1. Randy

    I bought a bow rated 55-70 pounds draw and 75 Percent let off I used a bow scale says it is at 55lbs which I wanted but at let off I’m holding 22 can this be lowered I hunt not a target shooter

    • Geoff

      Hey, Randy – To reduce the let-off you can adjust the draw length or the draw stop. By doing it that way you can decrease the let-off without changing the draw weight. Hope that helps!