Buckshot and slugs don't have specific assigned colours, it depends entirely on the manufacturer. For example, standard Remington 12 gauge shells are green, and standard Winchester 12 gauge shells are red, whether they contain buckshot, birdshot, or slugs. You could even buy various 12 gauge shells and make a rainbow from the collection.

You forgot to account for deceleration of the bullet; something which DayZ simulates. In real life, muzzle velocity of the M4A1 with M855 ammunition is 2900 ft/s (884 m/s), but the bullet at the muzzle experiences a deceleration of 900 m/s², or 92 Gs.

https://i.imgur.com/5z2wTpv.png

https://i.imgur.com/5z2wTpv.png

https://i.imgur.com/5z2wTpv.png

In T125245#1613872, @jakon72 wrote:

As far as realism, ammunition is M80 ball, not the most accurate.

Is there a chance that we could see different types of .308 ammunition in the future? Maybe not just different types of .308 but variants of other types of ammo as well? That would be amazing and would add a lot of depth to the combat in DayZ.

The Winchester Model 70 has dispersion = 0.001 and the hunting scope adds -0.00025 for a final dispersion of 0.00075, or 2.6 MOA.