Case Study: Airsoft Hop Arm

Mechanical Design

We were approached by a local Airsoft supplier/servicer with a request to help re-design a mechanical solution to help improve the range of ball-bearings (BB’s) fired by a marksman’s rifle. They hoped to avoid replacing all the internal mechanisms with expensive high-end components and required a simple, low-cost alternative. After an extensive collaboration between our design engineers and the customer, we came to the conclusion that we could make vast improvements in range if we amended the design and material of the hop up arm.

Mechanical Design

The Hop Arm compresses the Nub into the Bucking around the Inner Barrel. When a BB is forced past this compression point, it creates backspin which improves accuracy of shot as well as allowing the BB to fly for longer distances. This Hop Arm has a slot connected to an adjustment slider that dictates how much “hop” is applied. This coupled with heavier weight BBs (0.30g – 0.50g) creates a stable, fairly wind-resistant shot, capable of travelling greater distances.

Unfortunately, heavier weight BBs require a much stronger compression force to create the required backspin. The geometry of the original arm, in addition to its plastic construction meant that it could not stand up to the greater forces necessary. The original arm provided by the manufacturer utilises a 0.25g BB and has a range of 50m.

Mechanical Design

After receiving the original Hop Arm from the customer, our mechanical design engineers worked to improve the geometry and material in order to increase functionality. HGL Systems has years of experience milling and finishing aluminium using our CNC machines as we favour this material for our own electronic enclosures. We felt the material would be a suitable choice to improve the hop arm’s stability and therefore improve shot repeatability and the parts life span.


• We slightly thickened the part to improve strength and reduce the chance of vibration loosening the Hop setting.

• We increased the angle of engagement for the adjustment slot running through the part. This would give the part much more movement down into the bucking, greatly increasing BB compression.

• We lengthened the “point” on the underside of the arm, further engaging the Bucking material.

• We constructed the arm using aluminium with a hard anodising coating.

Testing And Customer Response

We were able to install the new part and quickly reassemble the rifle before returning it for testing. The test rifle was fired 100 times to ensure the part wouldn’t move or lose its Hope settings. It was tested firing 0.25g BB’s up to a whopping 0.45g BB’s. A range test showed the extra compression generated from our improvements, paired with the now heavy-weight ammunition, added a staggering extra 30m to the shot. Our customer was incredibly satisfied. They now have a hop arm that will not break, can be used with heavier, more stable ammunition, with a comfortable 80m range.

Find Out More

If you have a design concept, HGL Systems would love to work with you to help refine the design and manufacture your product. Please get in touch today.

Follow Us

Subscribe to Our Blog


  • News

Latest Posts

  • New CO2 Laser Cutter
  • New BGA Rework Station
  • New High Speed Pick & Place

HGL Systems Ltd, Acorn House,
Lindum Business Park, Lincoln