I got inspired when I saw the grapple gun from the Hl2 mod Ivan's Secrets, so I decided to give it a try myself. It's not 100% accurate to the reference image used, but close enough:P
Update1* Made a new stock. This is also not 100% accurate to its reference.
Update2* Finished most of the meshes. Some minor details and the projectile left to do. At last I'll optimize it.
Update3* (Picture 3,4) Finished all the meshes. Now it's time for optimization.