Here I am with my recently purchased (used at a very nice good price!) Colt 1851 Navy Sheriff revolver. I like this pistol a lot. It may have been in the hands of the 8th Missouri. It is hard to say, as many soldiers brought their own pistol from home, if they were to have any firearm at all.
If not, it is likely that the standard Navy revolver (slightly longer and heavier than the "Sheriff" model pictured) was even the 1861 Navy. Both are .36 caliber. I haven't fired the weapon yet, but look forward to doing so soon. I must saying the holding this Colt, I find it very pleasant and seemingly a joy to use. I like my Enfield rifle too, but the pistol just seems more natural to me. Maybe it is that cavalry blood from my ancestors flowing in my veins!