Didn't cause any harm.
***I dry fired an M1 rifle endlessly in basic training in the Army.***
Same here with the M-16 and M1 carbine.
I did break the firing pin of a H&R single shot 12 ga shotgun when I dry fired it.
Never dry fire a .22 as the firing pin can damage the rim of the chamber.
As them boys said in the video, it’s OK to dry fire some firearms, and others only with snap caps, and still others NEVER. Someone else’s (including those belonging to me) falls in the latter category.
You can dry fire your own as many times as it takes to keep in practice, and on many firearms it will not cause any harm. I use snap caps with spring loaded “primers”.