I don't get the premise here - are we being asked if 'Custer's last stand' is a 'myth', is somebody else suggesting that it is, is somebody else suggesting that it isn't - and what do the rifles have to do with it?

None of Custer's men who might have witnessed his end lived to tell about it - but over the intervening years, much of the action has been 'reconstructed' from contemporary accounts - including those of Sioux warriors who were there - battlefield excavations, letters, etc. So ... what is the question, again?