Ordnance explosions have physiological impact. Depending on the type of ammunition and the distance between a soldier and the impact, explosions can cause stun effects like ear ringing, fuzzy optics or unconciousness.
Ongoing development 
ACE 1.13 RC5 [2011-12-09. Hotfix: 2012-04-27]
Stable
ACE 1.13 for OA [2011-12-23]
ACE 1.3 for A2 [2010-07-05] (Deprecated)
Dev blogs
Wheeled by Wagn v. 1.8.1