The ARES M4 Sniper-1 has a 276mm Free Floating Rail System with plenty of space for accessories. It comes with battle sights which you can remove and replace it with something else. Inside is a Metal Gearbox from the ARES 2013 days which is perfectly capable of running an 11.1v battery.
Speaking of batteries, the housing for it can be found in the stock tube which is covered by a Magpul PRS ergonomic stock which can slip and slide to points which best suit its user.
Within the free float quad railed barrel is a Aluminum 475mm Outer Barrel, the preferred length to pick off distant targets. It shoots consistently with precision as it should do if you were to use this in a sniping position.
You would most likely shoot this in semi auto, but it has full auto just in case. For that you'll need a mid cap magazine accommodating 130 6mm BBs each being fired at around 400FPS which should keep the opposition busy trying to find you!