They're guns available in ARMA that just aren't enabled as possible spawns in DayZ. If it isn't in ARMAII/Arrowhead (including BAF, Czech, and PMC expansions) it simply can't be spawned. There's no way to add custom weapons because it would require every other user on the server to have a mod installed. You can execute scripts on other players but you absolutely can't force another player to somehow download content that isn't already in the game.
Dayzgrail, there is no such weapon in ARMA so you're out of luck. There are thermal sniper rifles (M110 and AS50 TWS) and a silenced sniper rifle (KSVK) but there literally isn't a silenced thermal long rifle in the game.
About other hackers
in Offtopic & Spam
Posted
They're guns available in ARMA that just aren't enabled as possible spawns in DayZ. If it isn't in ARMAII/Arrowhead (including BAF, Czech, and PMC expansions) it simply can't be spawned. There's no way to add custom weapons because it would require every other user on the server to have a mod installed. You can execute scripts on other players but you absolutely can't force another player to somehow download content that isn't already in the game.