Such meticulous attention to detail has led some mainstream re-enactors to nickname their progressive brethren “stitch-counters.”

“They get a little bit elitist in their attitude and they can be a little snarky at times,” said Dennis Rohrbaugh, a contractor from Chambersburg, Pa., who’s leading about 150 re-enactors to the mainstream event produced by Civil War Heritage of Gettysburg, Pa.

Rohrbaugh said mainstreamers and progressives share plenty of common ground, but there’s only so much realism he can stand.

“Just because soldiers at the time had dysentery doesn’t mean we have to go out and have dysentery,” Rohrbaugh said. He’s not above hiding a cooler at camp to keep food safely chilled.

Civil War Heritage leader Kirk E. Douglas Sr. said the rules are looser at his mainstream event because it’s a show for spectators. People might come for the 68-gun artillery battle and the Civil War Balloon Corps – although there were no hot-air balloons at Antietam – and learn something in the process.

“The history program far exceeds the four hours of battles that we’ll have,” Douglas said.

Christopher L. Smith, a re-enactor from Akron, Ohio, said the dual re-enactments evenly divided members of Birney’s Division, composed of 24 Federal infantry re-enactor units in four states. Smith led a group to the progressive event, while Rohrbaugh headed the mainstream faction.

Smith said the competing events caused confusion in the ranks.

“From a personal standpoint, I’m not necessarily pleased about it, but people can do what they want to do,” he said.