If you want your M4 to have a genuine GI-type sling, do what us military folk do: Buy the sling that works the best for you and throw the issue one in a duffel bag until you turn your weapon in at the end of the deployment. Nobody uses that top-sling kit anymore.
"If ye love wealth better than liberty, the tranquility of servitude than the animated contest of freedom, go from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains sit lightly upon you, and may posterity forget that you were our countrymen!” - Samuel Adams