I've played through most of Half-Life, and I believe these require a lot of improvement.
You should have a second model set for Third-Person mode, without hands, and only the First-Person model has hands, since in the other views it automatically mounts to the hand. Trust me, look through the code, there are ways to do this.
Also, the hand models might be able to be called from the actual hand model itself, and the two hands would move and mount to the point on your weapon in third-Person. I'm pretty sure that it's possible.