A little background on his rifle. ISAF (the coalition of Western countries in Afgh) forces were being engaged by Afghans in fire fights where the common rifleman was not equipped to fight at such long ranges. The Taliban and other insurgents were using rifles, some as old as the late 1800s to engage us from long ranges. The M4 has a maximum range for a single target of 500 meters. The ancient, rusty, and unreliable, the Taliban used rifles like that of the one your bust is using, that could easily range out to 800 meters. While our heavier machine guns could reach out to these ranges, the majority of soldiers would be neutralized before the fight even began. Therefore, the Army started giving each Squad Designated Marksman (SDM) a modernized M14, improving our ability to respond to long range ambushes occurring in mountainous passes and other dangerous terrain.
It is interesting to me that such old, outdated weaponry provided such a tactic advantage to the Taliban. I'd be interested to know the make and model of the one used in the pic above, but it looks like the sculptor got it right.
EDIT: apologies for failing to edit this before posting. I think it's understandable, but it does not sound like I intended it to read.