'Saluting' across the chest

SGT Richard H., as long as they recognize it as an Officer that is in the vehicle. It used to be that you would have the blue DoD sticker and they defaulted to that. There are still some left, but a lot have been scraped off since they stopped requiring them ~3 years ago (some took a while to phase them out though).

COL Randall C. I think the Navy base here does 100% ID check now...I assume that's what most posts are doing, right?

SGT Richard H., correct (so yes, if the gate guard is military and recognizes the driver or someone else in the car as an officer, they should render the proper military courtesies, unless they've been instructed not to because it would be impractical [I'll leave that up to their supervisor])

One side note is that many of the gates around here (in the NCR) are manned by DES civilians, and I would suspect that might be a trend elsewhere as well (previously it was a push to go with contract guards, now it's migrated to DES civilians).

There WAS an across the chest salute. Now whether that is some how connected to what you are seeing now I do not know, but it is possible. At one time and I can't verify when it came into existence there was an across the chest salute. In addition to having served in the army I am also a Civil War Re-enactor and during that period they used an "across the chest salute" when they were under arms particularly when they were at "shoulder arms". When holding the weapon at "shoulder arms" (which the rifle is held in the right hand by the trigger guard, vertically and parallel to the body) according to "Hardee's Light Infantry Tactics" the salute would be rendered with the left hand across the chest. Just something to think about.

Same with a rifle at Shoulder Arms.

This is the explanation I was always given.

That is almost the motion I'm talking about, except gate guards typically keep their hand open and flat just like you would when rendering a regular hand salute instead of making a fist.