I have an older collapsible stock (M4 style) that I put on one of my 870s years ago.  It was a less expensive model (probably ATI) that I can't find an exact copy of to show for reference, which is a good thing that they don't make that model anymore.  The problem is it changed the angle of the gun upwards a little bit, but noticeably.  By that I mean no matter how it's adjusted, I'm looking partially at the top of the barrel/bead sight instead of through it for a perfect sight picture.  I like the idea of the collapsible stocks and would like to get another one (probably a Blackhawk), but do they do the same thing or do they line the gun up correctly?  Thanks in advance.

The Blackhawk stocks do line up very well (in my experience)

The stock angles downward, which gives you room for a proper cheekweld to look down along the length of the barrel from behind the receiver, instead of being straight line which puts your head too high to look down along the top barrel, instead of along the length of barrel as it should.

BIGGER_HAMMER

Mesa Tactical makes two versions of their collapsable stock adapter.  One is designed for taller sights or something mounted on Picatinny rail, the other is made for OEM bead sight.

Here's mine, designed for bead sights.
Attached File

Choate makes a few that sound like what you are looking for.