Case Study: Rear Sight

Process: Metal injection molding
Secondary Processes: Tapping and nitride finishing
Density: 7.5 g/cm³
Tensile Strength: 380 MPa (55,000 psi).

2011 Award of Distinction: Rear Sight
2011 Award of Distinction: Rear Sight

End Use and Function

A rear sight used on sporting and military rifles such as the AR-15, M4, and M16 models. Complex part geometry drove the need for an elaborate tool design with tight tolerances making metal injection molding (MIM) the most costed effective and high-quality method of production.

Fabrication

The nickel steel MIM part features extremely close tolerances and a complex geometry requiring an elaborate tool design. The sight allows the shooter to target objects at ranges up to 183 m (600 ft.) by using the larger aperture and to target objects at longer ranges by flipping the sight down and using the smaller aperture. The part is made to a density of 7.5 g/cm³ and has an as-sintered ultimate tensile strength of 380 MPa (55,000 psi).

Results

  • Choosing the MIM process over investment casting provided a 40% cost savings. This part is traditionally manufactured through investment casting process followed by significant and expensive secondary machining operations.
  • Return on tool investment for customer in less than one year