Ok, having looked at the film, I have a suggestion: The final pose that you have him in is unnatural. The gun shouldn't end up exactly perpendicular to his shoulder line. There are several ways you can fix this, the easiest of which would be to twist his chest so that HIS right shoulder goes back a bit and his left shoulder comes foreward. that should eliminate the need to overextend his left arm, making the elbow lock up like that. you've definitely got to twist the chest, at the very least.(of course, twisting the chest is going to mean repositioning the final keyframe for the gun, so that it still points where you want it.) For something a bit more dramatic, instead of twisting the chest, twist the hip, spread the legs a bit, drag the right foot back, and lower the hip a bit to bend the knees. And make sure his head still points foreward... If you want, I'll tweak the file you uploaded, and send it back to you, so you'll see what I was talking about.