The M16 is an assault rifle that is a .223 caliber / 5.56 mm. like any weapon it is only as accurate as its shooter, <><><> It can be very accurate.
No You could build a rifle in .306" or any other caliber but you are likely referring to 30.06. A 30.06 rifle is referred to as "30 Caliber" but to be accurate it is nominally .308"
Provde the caliber.
In all likelhood, one of the bolt action pistols in a rifle caliber, such as 6mm. That holds the accuracy record for a rifle, and would likely do so for a pistol.
200 yards
In excess of a mile.
900 meters, depending on the rifle, sights, and skill of the user.
You would have to define what accurate means to you- but in general, Ruger makes good, accurate firearms.
Depends on the load and range.
Your rifle is a Marlin Model 81. Value could range from $50-$145, depending on condition. Most are around $100 or so. Accurate reliable hunting grade rifle.
About 300 meters, depending on the rifle, sights, ammo, and skill of the shooter.
If you mean a rifle chambered for the .50 BMG cartridge, such as the Barrett M82, the EFFECTIVE range is about 5,900 feet. The rifle weighs about 30 pounds, and sells for about $9,000.