5th Infantry Division (Mech). Division change of command ceremony, early 1990s. Fort Polk Louisiana. Battalions in a row across a huge hot-ass field in blazing, humid Louisiana heat.
Division adjutant puts the division on rest while we're in between practice run-throughs of the ceremony. Aviation guys off to one side of our infantry battalion pop their helmets off and swig water like crazy. Nearby tanker battalion was darn near naked within 10 seconds of the rest order. But not 4/6 Infantry 'Regulars'!
We stand there with helmets strapped tightly to our noggins except for two guys up in front of me. We watch in slow motion horror as their chin straps fly free with an audible pop. Either they had forgotten they were Regulars or the heat had gotten to them. No difference. The battalion sergeant major had climbed up through the battalion formation(while we all had slung rifles and fixed bayonets in place) before anyone could gasp in shock.
"Why are you two ********** so squared away and the rest of us are so ******* up," he asked in a growling yell that would make drill sergeants cry. In the instant the two poor excuses for could snap their chin straps back on, the sergeant major wheeled inside the formation. Chevrons reflected in his eyes.
"And why does the sergeant major have to come correct these clowns when I've got NCOs standing all around them?!!!!" The other battalions were certainly impressed with our prowess and helmet-wearing discipline that day. Or at least I think they were talking about that as none of them were falling out for heat stroke. Weaklings.
Back on topic, I'd never heard that thing about the chin strap and artillery. I will say that we mocked the SQT manual cover from the 80s that had a grunt firing while on the run, his chin strap flying free and boot laces streaming in the breeze. We knew no 'Regular' had posed for nor had been consulted on the accuracy of such an illustration.