The effects of short glass fiber (SGF) mass fraction on glass fiber orientation, residual wall thickness, and pressure resistance of pipe parts formed by gas-powered projectile-assisted co-injection molding (G-PACIM) were investigated through experiments. The results show that the fiber orientation is better in the outer near-interface layer and intermediate layer, while the orientation is the poorest in the outer layer near the mold wall. As the SGF mass fraction increases, the fiber orientation at the same location gradually worsens. For G-PACIM pipe parts with 10% , 20% , and 30% SGF/PP as the outer layer material, the wall thickness shows a consistent trend along the penetration direction, the total wall thickness and inner layer thickness decrease, while the outer layer thickness increases. For pipe parts with 40% SGF/PP as the outer layer, there is no obvious trend in the total wall thickness along the penetration direction; however, the inner layer thickness decreases and the outer layer thickness increases. As the SGF mass fraction increases, the total wall thickness and outer layer wall thickness first increase, then decrease, and finally increase again, whereas the inner layer wall thickness continuously decreases. The pressure resistance of the pipe parts increases continuously with the SGF mass fraction, though the rate of increase varies.