Well,what Phil just said shot down my normal "AK" Responce. If the government indeed engages in democide,then yes,an AR-15 would definatly be my choice.
However,under normal circumstances,for a Long range weapon under 1000,heres my list
Bolt Action: Mosin Nagant M44 Carbine,a few good mods,pick one up in imaculate condition for about $200,Ammo is cheap,Maintainance is simple.
Semi Automatic: M1 Garand,Simple to maintain and fire,excellent stopping power,ammo is Milsurp. Accurate.
As for tactical AK-47 or AR-15,both are readily available,both have mods left and right,both types of ammunition are readily availible,and both are dependable,reliable guns. Ive seen Great shape AK's go for about 400,and new Ars go for about 600-650 range.