InRange TV has video of Forgotten Weapon's Ian McCollumn interview of an AR-15 designer Jim Sullivan. The latter half of video has how the improvement Jim Sullivan has worked on would make difference on M4.
https://www.full30.com/video/9b50f8a825ab510b4c227c7b32a76bc1
The Firearm Blog also shows some other guns Sullivan worked on and link to Small Arms Review Sullivan did some years ago.
http://www.thefirearmblog.com/blog/2014/12/01/two-interviews-designer-ar-15-l-james-sullivan/
From: Full30, The Firearm Blog
