Wrong firearms for the time period

I'm always astonished how inaccurate Hollywood continues to be at depicting accurate time-period firearms in Old West movies.
In the Civil War western, A TIME FOR KILLING, the time period is late April through May 1865. The Civil War has just ended.
Yet the movie's characters are shown using firearms that are anachronistic.

1) Allin trap-door carbines. These were not in use with the post-Civil War Union Army until early 1868.

2) Winchester lever action 1866 and 1876 short rifles

It would have been more accurate if the following firearms had been depicted.

1) 1860 Springfield muzzle loading rifle muskets.

2) Spencer, 7-round repeating carbines.

3) Possibly Spencer, 7-round repeating rifles, but only some 12,000 were manufactured for the Union Army.

4) Sharps falling block, single shot carbines. These were in common use with the Civil War Union Army and were widely used at the start of the Battle at Gettysbury by Brigadier General Buford's cavalry 9th Division. His small force of 9,000 troopers were able to hold off two Confederate divisions because the troopers used the Sharps breech-loading carbine which could fire 6 to 8 rounds per minute, compared to the 3 to 4 shots of a muzzle loader rifle.