I'm going to agree with Hitzy... if you plan shooting that thing regularly, the concussion will most likely damage the phones internals.
To ensure your electronics won't die, you want something with this rating:
MIL-STD-810G certified (48” drop, shock, vibration, blowing rain, sand and dust, water pressure, drip exposure, altitude, freeze/thaw, high/low temperature, temperature shock, humidity, explosive atmosphere, salt fog, contamination by fluids, solar radiation, fungus, acoustic noise, acidic atmosphere, gunfire shock)