Best rifles for a resistance. While the ubiquitous AR is popular and has the most options and accessories for sale, I'm more of an AK/SKS fan since the 7.62mmx39 is better for hunting than the .223/5.56mm. The .223 has greater effective range but is still a lightweight bullet, even if using soft point or hollow point. Great for inflicting casualties on enemy troops, but not as great for knockdown power.
In a resistance, guerrilla tactics would be use. Mostly hit and run since large conventional engagements would be unlikely unless there was a second civil war with states fighting each other. As such, it'd a be quick ambush picking off the leaders and then hightailing it out of there before the AI drones homed in on you. LOL
In that case, a simple, high-powered bolt-action rifle with scope would be both sufficient and allow the resistance fighter(s) to be further away from the target. One of the most common in the US is the Remington model 700. It's used in the military and law enforcement as a sniper rifle and comes in several calibers. For commonality reasons, I'd recommend the 7.62 NATO round/Winchester 308.
That said, any high powered, scoped rifle and a few hundred rounds of ammunition will do since, using guerrilla tactics, only one or two rounds will be fired per engagement. It's better to be proficient with a cheaper rifle than lacking experience with a more expensive one.