The Model 1873 .45-70 "Trapdoor" Springfield rifle was standard issue to the US Army in 1876. As Cavalry, the troops would have been using carbines -- some longer range sporting rifles were personal weapons of various officers. Benteen's forces would also have been destroyed had not the ammunition train arrived too late for Custer but just in time for Benteen.

As for repeating rifles the number among the Cheyenne and Lakota was probably very small. Ammunition was a problem and so many were armed with muzzleloaders. The real question is, "Who is buried in Custer's grave at the US Military Cemetery at West Point?" When the bodies were collected there were only skeletons left, making identification difficult. Animals had dragged body parts around, intermingling Indian and Cavalry, so -- who IS in Custer's grave? Some of it could be horse bones.

Go visit the battlefield, it's open to tourists and I've been there. It's quite and eye-opener.