I took the default King Arms M4A1 (rear-wired Canadian version), and did the following:
1) Replaced gas block with quad-rail segment, placing a Surefire 300 lumen light on the bottom and a flip front sight on the top.
2) Replaced carry handle sight with flip rear sight and EOTech XPS 2nd generation holosight.
3) Installed 20mm rail on the bottom of the classic clam shell hand guard, affixing an AFG2 foregrip.
4) Replaced the factory 14.5\" inner barrel with a 10.5\" barrel.
5) Used velcro tape to attach a sling to the butt stock to achieve a \"straight-down\" transition hang.
The result? A real gem of a CQB rifle.