[GigaBuist]

I snagged a Mossberg 18.5" cylinder bore 870 barrel some time ago and threw it on my 870 Wingmaster this weekend to give it a go.

Here's what I found confusing: The rear sight flips up and down. I have no idea why anybody would want that feature. At first I tried with the rear sight in the down position, just using the front post like a bead, but that didn't feel quite right.

So, with rear sight up I gave 'er a go and things felt a lot better, less like I was just guessing where I was really aiming.

Still, seems like I'm missing something here. Why the choice?

[Carl N. Brown]

The folding leaf sight is dovetailed to the ring near the breech
end of the barrel. A dovetail groove /__\ is the simplest way
of mounting an open sight on the barrel and the thickest part
of the barrel is near the breech. The rest of the shotgun barrel is
too thin for a dovetail. The folding leaf rear sight is about the only
type of dovetail sight that will fit there.