Acutaly, using contemporary firearms could work.
1. A solid projectile can't be deflected back at you with a lightsabre. It will only be desintegrated.
2. Modern aussault rifles habe far higher muzzle velocity and rate of fire than SW blaster rifles were ever shown to have in any work.
We all know, Jedi and Sith are not invincible. Fire enogh blaster bolts at them, and their defence will be overwhelmed. With a modern assault rifle blasting projectiles with a velocity of 900m/s at 900rpm, I seriously doubt any Jedi or Sith will be able to mount an effective defence.
Fire from more than one point at once and even Luke Skywalker will be finished.
I have to disagree.
1. True a solid projectile cant be deflected back at you, but it can be blocked by the lightsaber.
2. Never underestimate a Jedi/Sith's reflexes and their ability to block using the lightsaber. Furthermore we dont actually know how fast a blaster bolt is, you said it yourself in the movies the average blaster bolt is not seen to be that fast but that was only because of the restrictions of the movie's special effects. I am not saying that a blaster bolt will have the same velocity as a modern assault rifle, but the difference between the two is not that big. And again I'm going to say that a powerful Jedi/Sith can easily block ANY incoming attack by simply using the force as a shield. As seen in the "Return" trailer when the Sith Pureblood master of Darth Malgus is able to block the missile fired at him from the Trooper, by simply shielding himself with the force.
All of this said I am not suggesting that Jedi/Sith are invincible or unbeatable, I am simply stating that having a modern assault rifle will NOT guarantee you a victory over a Force user. It might give you a slight advantage(faster bullets which wont be deflected back at you) but apart from that I really cannot see how having an AK with you means that you automatically have the upper hand versus a Force user.