ALL that I use are open sights, and out to 100 yards, BUT I'm blessed with very good distance vision for my years, it's reading small print instruction manuals and food labels that mess with me...but back to the topic...,
There are several sorts of "open" or "iron" sights. There are the fiber optic or even tritium enhanced ones, but I've found them to be a bit on the crude side, so you don't get as much accuracy as you would get from other sights. There are the open sights, the classic open rear in back (V) and front sight post (I). That's what I use, though I have a thin, silver front sight post that shows up really well in low light. Then there are peep rear sights, some replace the factory rear V, and some are tang mounted.
https://www.brownells.com/search/index.htm?k=marlin+xlr+rear+sight&ksubmit=y. You should be aware that peep sights with small openings get tough to use in low light, and peep sights with large openings need some care to get a good sight picture.
So the first thing I'd do is look over your sights in low light..., since many ranges don't allow targets shot early in the morning, you will probably have to wait until near sundown at the range to do this. Determine what you can see, and then how well the sights work for you in low light, for what you see with both eyes can be different when you move to one eye looking over the iron sights.
Most folks forget that in low light, as the ability to see color diminishes, you use more rods in your retina which are just a tiny bit away from the center of the eye where the color vision is located, and so you will tend to be off on impact compared to what your rifle did for you on the range in bright sunlight. At 100 yards or less this might not matter as it does at say 300 yards.
IF you find you, as you suspect, that you don't like the low light and iron sights, then you
know you want a good scope, that does an excellent job of
gathering light. Even with my nice distance vision, there have been times when I could see the deer with both eyes, but when I concentrated on one eye and the iron sights, it reduced the light just enough that the animal blended into the background and I couldn't shoot. A nice, light gathering scope would've made all the difference. I'd look at light gathering ability first, then worry about magnification amounts.
LD
