If you want an accurate measure of time, just code an animation correctly. On the battlefield (or in a blank-fire section attack

) you generally won't go from running to jumping straight onto your face. The way its generally done is to fall to your knees and from there let your body fall forward onto your stomach/elbows. If you keep the animation the way it is now and simply "lock" the weapon for a given amount of time, people will complain. Now if you animated it properly, and had the character hold the weapon across his chest and fall to his knees then elbows, and then align himself for aim, I think this idea would be far better received.
On the note of going prone, please remove the ability to move sideways with the iron sights up. Its just not possible.
And another note, there should defenitly be a maximum elevation that you can shoot while prone. Like the tank turret has a maximum inclination, the same applies in real life to a person firing from the prone. The purpose of the prone position is to minimize your profile (IE your size as a target) and provide a stable firing platform via bracing yourself with your elbows. I just got down on the floor and tried this and I'd feel safe in saying that a maximum elevation for firing from the prone position would be about 35 or 40 degrees. Get down and try it yourself.
-Scott