[Prodigal Son]

The reason the SAW is effective out to that rate is because it's spraying out a high volume of fire. Technically, the M16 is good out to that range if you can see what you're shooting at and can see where the rounds land. The maximum range of the M16 is over 3500 meters. Effective range is only 550 though. The 50 Cal has a max range of over 6 kilometers but the effective range is 1800 meters. That's over a mile. The thing with the 50 is, you can legitimately aim at things that far away and hope to hit it.

The barrel for the 50 is almost 4 feet long. This accounts for most of this accuracy. The thing with the M4 is- you're losing barrel length. That's what makes it less accurate than the M16A2 at range.

[CGTRWK]

Barrel length has no effect on intrinsic accuracy. The only benefit of a longer barrel is a longer sight radius with iron sights. Actually that's not entirely true, you also get reduced wind drift and bullet drop from higher velocity - but going from a M16A2 to a M4, it's not enough to matter.

That's probably the problem - M4 iron sights are no good at a distance.

[jwh_Denver]

The barrel for the 50 is almost 4 feet long. This accounts for most of this accuracy.

Would it be feasible whatever the barrel length of military rifles to put threads on the end of the barrel allowing for an extension barrel to be put on for longer distances? Obviously you would want some kind of thread quard.