It would be realy cool to see some realy heavy guns in ARMA 3 like the NTW 20 Rifle.It is a 20 MM Anti Material Sniper Rifle designed to destroy strategic objects like radar,jets,command-vehicle,etc.The weapon features a 20MM barrel with explosive ammo for ranges up to 1200 meters,and a 14,5 MM for distances over 1700 Meters.It would be great to see this weapon ingame when its final released,but because of the huge size of weapon,it is not possible to fire this weapon alone with deadly precision.So that means that you need a Special back pack for the sniper rifle system,then you have to put all pieces barrel,reciever-section,bypod ammo etc.Then you have to carry the weapon to your sniping location and there you have to put the weapon together,with full animations,it would take you 30-35 seconds to deploy the weapon,with the barrel you wanna use 20MM or 14,5 MM.And to be sucessfull you need a spotter with a range finder,who is giving you the range distance to adjust the scope for the perfect shot.
Here is a little video with all informations about it