Airsoft hop-up: what it is and how to adjust it

Hop-up is the setting that changes range and accuracy the most. It doesn't add power: it gives the BB spin so it flies straight longer. Here's where it sits on different guns, the adjustment types, the buckings and how to set it.

Updated 2026-11-08 · 2896 replicas in the database

How it works

At the start of the barrel sits a rubber bucking with a small nub. An arm, driven by a wheel, a lever or a screw, pushes it down: the BB rubs against it on the way through and leaves with backspin. The spin creates lift, like a sliced tennis ball, and offsets the drop.

Turn the wheel (drag it or use the mouse wheel) or the slider, then press Fire. In Auto hold for a burst and pick the ROF. Previous shots stay grey for comparison.

orange: the part you adjust · dark red: the bucking

Where it is on different guns

The hop-up is always in the chamber, where the BB enters the barrel, just ahead of the magazine. What changes is how you reach it.

M4/AR15 AEG: through the ejection port. Open the dust cover (and pull the charging handle if needed): the hop-up wheel is right there.
AK AEG: under the top cover. Remove it: there's a lever that slides back and forth, or a wheel on newer models.
GBB and NBB pistols: under the slide, behind the barrel. Adjust with the slide locked back or removed, using a wheel or a small key depending on the model.
Bolt-action spring rifles: ahead of the bolt. Pull the bolt back: the wheel or lever is reached through the port.

On gas rifles (GBBR) you reach it like on AEGs of the same platform, with the bolt locked open. Always check the manual: some models have their own design.

Adjustment types

Rotary: a wheel with a cam pushes the arm. Fine, progressive adjustment; the most common system on modern AEGs.
Lever (sliding): a lever slides a wedge over the arm. Typical of AKs and many older guns; it moves in clicks or smoothly.
Screw: a screw pushes the arm directly, adjusted with a small key. Common on pistols and some spring rifles.
Fixed: bucking pressure can't be changed. Found on budget pistols and simple spring guns: works well with one BB weight only.

In the database 2151 spec sheets list an adjustable hop-up and 224 a fixed one; 65 specify a rotary system.

The bucking

The bucking is the part that actually spins the BB. There are many shapes (single contact, long contact, double contact, R-hop) and hardnesses, and they must fit your gun. In short: in winter a softer bucking is recommended, because cold hardens the rubber and reduces the effect.

Full guide to hop-up buckings →

How to adjust it, step by step

  1. Use the BBs you'll play with: each weight needs a different setting.
  2. Start almost closed (little effect). Fire a few single shots level, at a target 30–40 metres away.
  3. Add effect a little at a time, firing 3–4 shots after each change.
  4. Stop when the BB flies straight and rises only slightly near the end. If it curves up ("banana"), back off a bit.
  5. Check again after some shots: the bucking settles and may need a small touch-up.

Common problems

Hop-up slows the BB slightly, so chrono with the hop-up already set. For BB weight see the BB guide.

FAQ

What does hop-up do?

It puts backspin on the BB: the spin creates lift so the BB flies straight longer instead of dropping.

How do I know it's set right?

The BB should fly straight and rise only slightly near the end. Rising a lot means too much; dropping early means too little.

Does hop-up change FPS?

Slightly: more bucking pressure slows the BB a bit. That's why you chrono with the hop-up set as you'll play.

When should I replace the bucking?

When it's hard, damaged or no longer holds the setting. Softer buckings work better in the cold, harder ones in the heat.

More guides

First airsoft gunPower systemsBB weightBatteriesChronographAEG maintenanceTransportHop-up buckings1 J limitJ/FPS converter