I'm with Alan. The clothing styles look late 1800s. I "grabbed" the photo and played with it in Photoshop. Their clothing is more suit style instead of uniform frock coat, sack coat or shell jacket. All the jackets have spread lapels. The ties are narrow and the shirts are consistent stand and fall collars. I didn't detect the possibility of any trap door rifles with my experimentation. Not saying that there were none. They all have fixed bayonets and a battleflag with very wide fimbration and no apparent border. And they ALL have on a medallion that appears round and suspended by a ribbon on their left breasts or lapels. Even the house looks "newer". Nice consistent squared corner bricks on the foundation pillars and neat siding and window trim. And very clean and sturdy stair risers and treads leading to the porch. Plus, war period photography left a reverse image. This one is "up right reading", buttons on the right and button holes on the left, rifles at "shoulder arms" or "right shoulder shift". I bet this is a pre-reunion group photo. These fellows are probably getting ready to board a train nearby and go visit with their veteran pards. Just my observations. Cool photo. Priceless family heirloom.

Keith