My grandfather passed not too long ago after going through his things I found an U.S. Springfield arms trapdoor rifle model #1844 which was manufactured in 1891 I also found an Hopkins and Allen double action #6 pistol these guns were not taken care of very well the pistol has some outside rust and the rifle has some rust inside the barrel I would like to know if there is any way to clean these guns and if there is what is the best method I would appreciate any help with this

There is no substitute for elbow grease. Use a bronze bore brush and some WD-40 to clean the Springfield barrel. Chances are that it's mostly had lead bullets through it, so bore cleaner won't be necessary. You may find some pitting under the rust. Those guns were fired with black powder loads. The pistol could be cleaned up with WD-40 too.