From a (fairly dated; 2006) Army Graphic Training Aid:
APPENDIX G - M16 RIFLE (5.56MM)
Unloading and Clearing Procedures
1.) Orient weapon in a safe direction
(Clearing container if available).
2.) Remove the magazine from the weapon.
3.) Attempt to place weapon selector lever on SAFE.
4.) Lock bolt to rear (ensure weapon is on SAFE).
5.) Inspect the receiver and chamber to ensure no
ammunition is present.
6.) With NO ammunition in chamber or receiver, allow the
bolt to go forward.
7.) Aim weapon into clearing container, rotate selector
lever to SEMI, squeeze the trigger.
8.) Charge weapon once.
9.) Place selector lever on SAFE.
I found the GTA at:
http://chemicaldragon.com/yahoo_sit...ng_Smartcard_-_Post_22_Jun_20061.22100850.pdf
Clearing procedures are roughly the same for the M4 series rifle.
These procedures also work for non-military semiautomatic rifles built in the AR-15 format.
You can also check out the ArmyStudyGuide website:
https://www.armystudyguide.com/cont...4/clearing-procedures-for-the-m4-series.shtml
The Army Study Guide is not directly affiliated with the US Army but, from my experience, it is frequently used by both Army board members and soldiers to prepare for a board and may therefore be consdered a reliable resource.