I think this is all a bit silly, the USMC established back in the 1970s that the short gas tube meant you got wider variations in pressure in the tube. The USMC refused to use the XM177 for this reason, and also because the barrel was too short, which also led to big variations in pressure at the gas port.
Hence the model 653 M16A1 carbine with the longer barrel, which led to the M4, which has a bit better gas system as a result, but it's still not as good as the longer tube.
The problems with the M4 are extremely well-known, it always has been and was designed as a PDW for support troops and people who needed compact weapons such as tank crew.
Why everyone keeps trying to use it as a front-line weapon for infantry let alone SF is utterly beyond me. It doesn't matter how thick you make the barrel etc. it's not up to the task because of the gas system, which is why H&K came up with the 416.
Personally I always look to the USMC when it comes to these issues, they came up with a better answer, spelt: "M16A4".