I have friends, who have been re-enacting for a long time who were in the movie in an artillery battery on Little Round Top.
I've watched that movie, oh, maybe 30 times or more. I know that scene well!
(Did you know they filmed that scene outside the park because of the monuments on Little Round Top, and the fact that they had to groom the ground so that no one tripped on twigs or stones?)
The last time we went to Gettysburg, our tour guide took us on a little extra trip to where the movie was filmed. VERY neat!