In 1850 we were still in the Percussion cap era with still a large portion of firearm being flint locks. To take a firearm back that jumps a minimum of 40 years (to smokeless powder) would not work out well. Heck even the machining processes didn't exist for any of the modern cartridge firearms.
I think the most likely result would be you get shot and robbed or just robbed of your magic new toys.
This ^^
As I was reading the responses I could see that people were missing the fact that back then they didn't have smokeless powder and the black powder just won't work in a semi-auto.
If you are taking guns to a manufacturer, take blueprints with dimensions.
Bear in mind that the steel back then was nowhere near the quality of steel today, and neither were their machining processes. You are going to need to avoid parts in guns that have sintered metal parts or are only possible with investment casting or processes like that.
You would probably want to take firearm examples from the fifties and sixties.
You could take double actions, but simpler ones, not anything that is too fancy.
The barrel would be about 4 to 5" long, and a lightweight profile. I wouldn't mind that it would be something like my 329PD in Scandium with regards to weight. I know they would not have titanium or scandium alloys back then, but they wouldn't have our steels either - what they need are the dimensions and I assume a working model to interest them enough to where they would be willing to reproduce it. Otherwise, it would be in stainless, but with a dark metal treatment, preferably one of the treatments that is extremely corrosion resistant and has high lubricity.
You should get with a firearms manufacturing historian and find out whether leaf springs or coil springs were easier for the manufacturers of the time to make, probably the former, but if the latter, I would consider looking at a Ruger SP101 or a Ruger Redhawk or Super Redhawk - certainly the original Blackhawks would be one I would consider.
The double actions or single actions would probably be something in .45 LC or .44-40 although those didn't come around until about 1870 or so IIRC - maybe they wouldn't be too far ahead of the ammo tech at the time.
As I said, I would not consider anything like a Glock unless I was sure I would live into the 20th century and could wait that long for smokeless powder and the acceptance of a semi-auto handgun, and even then I would more likely consider something that was all steel.
The rifle might be something like a Marlin 336 in .45-70 - maybe a takedown. It would have a short octagon barrel - ported. The stock would be rubber overmolded metal frame with a hollow buttstock for various goody storage - I am sure that the stock makers of the day could copy that in wood.
The nice thing about the .45 LC and .45-70 is that in the 1870s you could get that ammo (maybe the modern ammo would last you that long if you were careful), while at the same time you could take modern ammo back with you that is a lot more powerful and accurate. The ammo could be reloaded with black-powder.
The third gun would be a .22 rimfire of some sort. Yes, the predecessor of the .22 rimfire was present back then, so you should be able to eventually get a manufacturer to make the ammo. It could use black-powder and reproduce adequate performance.
It would probably be a fast acting bolt action (maybe a straight pull back), takedown - something like the Marlin Papoose, but in a bolt action. It would have a lightweight strong rubber over molded stock - again hollow - but it would be a slim stock so that it would fit in a pack. I would like a variation of the AR-7 design such that the barrel front could be placed in the buttstock - the barrel being short enough to do that (no worry about NFA back then).
