Case Study: Rifle Bolt

Process: Metal injection molding
Material: MIM-4605 low-alloy steel
Density: 7.5 g/cm³
Tensile Strength: 1,550 MPa
Yield Strength: 1,400 MPa
Hardness: 28–35 HRC

End Use and Function

This powder metallurgy component is a rifle bolt used in a Crickett 22LR rifle. To pass qualification testing, the component had to withstand 20,000 rounds of firing tests without any failure.

Rifle Bolt
2015 Award of Distinction: Rifle Bolt

Fabrication

Made via metal injection molding using a MIM-4605 low-alloy steel. The part’s design features many cross holes and undercuts, requiring complex side core matchings in the molding cavity. The part has a heat-treated density of 7.5 g/cm³, ultimate tensile strength of 1,550 MPa, yield strength of 1,400 MPa, elongation of 3%, and a hardness range of 28–35 HRC maximum.

Results

This single part replaced one produced by brazing together three machined parts, delivering an estimated 35% cost savings in the process. Additionally, using MIM resulted in 60% reduction in lead time. The fabricator delivers 60,000 pieces annually.