M4 carbine is more for urban warfare when beyond 250m is not a major concern and light weight is highly favour.
Does not matter -- 250 m or out further.
http://nssf.org/video/facts/MOA.cfm
A Minute of Angle (MOA) is an angular measurement.
A MOA is 1/60th of a degree.
1 MOA spreads about 1" per 100 yards. (actually 1.047")
1 MOA is a different size at different distances, 8" at 800 yards is still just 1 MOA.
Let us round off to 300 yds, or roughly 300 m, for now.
From the chart above, the MOA spread is about 3 in at 100 yds. Regardless of distance, the first thing any soldier do is to find cover, not concealment, but cover. If there are none, he will hit the ground and make himself as flat as possible. At 300 yds, your bullet will deviate about 3 in to any direction from your intended center.
A fully exposed human torso have a spread of 18-20 in, or 45-50 cm. So even if you are shooting at an enemy soldier who have no cover but is at ground, at 300 yds distance, your odds of hitting him decreased to less than 50/50. In this situation, any improvement in accuracy by way of a few additional inches/cm barrel length is pointless.
Keep in mind these are
PUBLIC information in the US where firearms are much more common than in your China. Not trying to be mean, just real.
Finally, am an Air Force guy who target shoot, not really a hunter, even though I have hunted before, deers and wild boars, and not someone like Gary who actually have been in combat.
But I was shocked French armed forces dump their FMAS and goes for the HK416 which has a very similar outlook as M4.
I have never fired a FAMAS, but I have fired a Kel-Tec bullpup.
Yes, it is an interesting rifle, but essentially a novelty rifle, and in my opinion, not a credible replacement for the standard automatic combat rifle when all things relevant to combat are considered.
I do not think PLA will favour a shorter range carbine style rifle as their standard army issue weapon.
And I predict the PLA will take after the French -- rid itself of the bullpup.
It will require a few yrs but once the PLA is fully appraised of the bullpup's disadvantages, it will replace it.
I may be out on a limb here...But I think the selection of the bullpup is more emotional than rational. Who wants to be like the Americans ?
There are many reasons why the 5.56 mm bullet remains popular despite many objections, from technical to emotional, leveled at it. Why 5.56 and not 5 ? Or not 5.55 ? Why 7.62 and not 6.62 ? Why the howitzer 105 and not 100 ? Look at the internal combustion engine for more examples. Why 2.2 liters and not 2.3 ? Why 50 cc and not 51 cc ?
The selection of the caliber measurement of 5.56 or 7.62 or 105 came from extensive testing, not just on destructiveness on the target but also on the user, as in maintenance and portability, and reliability under combat conditions. I do not care if I hit the enemy soldier with a 5.56 or 7.62. As long as he is disabled to the point where he can no longer contribute to the battle, I have succeeded. I will always shoot to kill, but killing is not my primary concern for him. So if I can carry more 5.56 rounds than I can for 7.62 rounds, I will take the smaller caliber any day.
Same reasoning for the selection of the standard or the bullpup config. Usage under real world conditions dictate the selection.
This is why -- in time -- the world's soldiers will rid themselves of the bullpup design and your PLA will be no different.
