Choosing ILF longbow limbs starts with three checks: the fitting on your riser, the assembled bow length, and the conditions behind the marked draw weight. A 40 lb label is a reference measurement—not a promise that every setup will measure 40 lb at your anchor.
This guide explains how to match longbow limbs to an ILF riser, read BOSEN LCS length and weight labels, and establish a repeatable setup before tuning.
Before you buy: an ILF longbow limbs checklist
- Match the fitting: choose the ILF or Formula version that matches your riser.
- Confirm the assembled length: check which riser the bow-length label refers to.
- Check the weight reference: record both the reference riser and draw length.
- Measure your actual draw weight: use your normal draw length and approved bolt settings.
- Confirm the string and arrows: match them to the complete setup, not just the limb label.
1. ILF vs. Formula: match the limb fitting to your riser
ILF means International Limb Fitting. It describes the attachment system, not the limb shape. Longbow-style ILF limbs can be used with a suitable ILF riser, provided the combination meets the limb and riser manufacturers' requirements.
BOSEN LCS limbs are offered in separate ILF and Formula versions. These fittings have different geometry and are not directly interchangeable. Select the correct version before ordering; do not assume one set fits both systems.
Check that each limb butt seats correctly under the tiller bolt, the dovetail engages in the pocket, and the limbs align with the riser. Follow the riser manual for bolt engagement and adjustment limits. Do not force an incompatible fitting or modify the hardware to make it fit.
If you are comparing handles, browse BOSEN ILF risers and confirm compatibility for your exact riser-and-limb combination.
2. Limb length vs. assembled bow length
Short, medium and long usually identify sizes within a limb range. An inch label may describe the assembled bow on a specified riser, rather than the physical length of one unmounted limb. Always check the model's reference setup.
For BOSEN LCS, the length labels and marked draw weights use different reference risers:
| Label | What it means | Reference setup |
|---|---|---|
| 68 / 70 / 72 inches | Assembled bow-length options, not individual limb lengths | 25-inch riser |
| Marked draw weight | Reference draw weight, not a universal value for every setup | 17-inch riser at 28-inch draw length |
Changing the riser changes the complete setup. Do not read a 68-inch LCS label as a guarantee of a 68-inch bow on every riser. Confirm the resulting bow length and required string before ordering.
At a longer draw length, string angle and finger pressure matter. A longer bow can reduce finger pinch, but length alone does not guarantee a smooth draw: limb design, riser geometry and the draw-force curve also affect the feel.
3. Longbow draw weight: measure at your draw length
The number printed on a limb is measured under specified conditions. Your actual draw weight depends on your draw length, riser geometry, limb choice and tiller-bolt setting.
Understand the bow draw-length measurement
ATA/AMO draw length is the distance from the string's nock groove to the grip's pivot point, plus 1.75 inches. A measurement of 26.25 inches to the pivot point therefore corresponds to a 28-inch ATA/AMO draw length. A measurement to the front of the riser is not the same reference.
Use a suitable bow scale, or ask an archery shop to measure the weight at your normal draw length. Record the riser, draw length, tiller-bolt position and brace height so you can repeat the measurement.
Why marked weight and actual weight can differ
A limb marked 40 lb on a 17-inch riser at a 28-inch draw should not automatically be treated as 40 lb on a 25-inch riser or at a 30-inch draw. There is no universal pounds-per-inch correction that is accurate for every limb-and-riser combination.
Choose a weight you can control through a repeatable anchor and a normal shooting session. Use tiller bolts only within the riser manufacturer's adjustment range. If the required weight falls outside that range, choose different limbs instead of backing the bolts out too far.
4. Match arrow spine and arrow weight to the measured setup
Start with the arrow manufacturer's selection chart using your measured draw weight, arrow length and point weight. Recheck the match and tune whenever you change risers or limbs.
Arrow spine and total arrow weight are different. Spine describes shaft stiffness; total arrow weight includes the complete arrow and its components. Follow the bow manufacturer's minimum arrow-weight requirement. An arrow that is too light can damage the bow; a suitable spine number alone does not establish a safe total weight.
Keep a setup record with your riser and limb models, draw length, measured draw weight, bolt positions, brace height, tiller, nocking point and arrow specifications. This makes future comparisons more useful than relying on the label alone.
5. Establish brace height and a repeatable tuning baseline
Set up the bow with the string, rest or shelf, and accessories you will actually use. Check alignment first, then change one variable at a time.
- Brace height: measure from the string to the grip's pivot point and use the approved range for your actual setup. Do not copy a recurve bow brace-height chart onto longbow limbs without confirmation.
- Tiller: compare the upper and lower string-to-limb measurements using the manufacturer's reference points.
- Nocking point: measure its height above square to the arrow support; check nock fit and clearance.
- String: confirm the correct length, material, strand count and serving for the complete bow.
Evaluate clearance, arrow flight, groups and sound together. A quieter shot by itself does not prove that the bow is correctly tuned.
ILF longbow limbs: frequently asked questions
Can I put ILF longbow limbs on a recurve riser?
Potentially, if the riser has the correct ILF fitting and the manufacturers approve the combination. Check limb clearance, alignment, safe adjustment limits and the required string. An ILF fitting alone does not confirm every aspect of compatibility.
Does a 68-inch limb label always make a 68-inch bow?
No. The label must be read against its reference riser. For BOSEN LCS, 68-, 70- and 72-inch bow-length labels are based on a 25-inch riser. Confirm the assembled length for other combinations.
Are ILF and Formula limbs interchangeable?
No. They use different fitting geometry. LCS is available in separate versions, so choose the version that matches your riser.
Does carbon construction guarantee a smoother draw?
No. Material is only one part of the design. Limb profile, riser geometry and the draw-force curve also matter, especially at your own draw length.
Choose your BOSEN LCS setup
Explore the BOSEN LCS carbon longbow limbs for current carbon-and-foam construction, fitting options and ordering details. To compare longbow-style and recurve options, visit the BOSEN ILF limbs collection.
Before ordering, ask BOSEN to confirm your limb-and-riser setup. Send your riser model and length, draw length, shooting use and desired draw weight. Ask us to confirm the assembled bow length, string specification and draw-weight reference for that combination.
Published by BOSEN BOWS. General measurement and tuning references: Hoyt Recurve Owner's Manual (2005), draw-length terminology and Easton Arrow Tuning Guide. Model-specific settings in those manuals are not BOSEN specifications.
