I used cheap bipod to zero my AR-15 on 25 yards. Here is my setup:
I put rubber covers on quad rail where I don't plan to attach accessories. Looks a bit bulky, but good for support hand.
When I started shooting I noticed that I'm hitting target way to high (I suppose sights were zeroed by default for 100 yards). So, it took several iterations to make it hit my target. I used 4" targets.
Finally, I detached bipod and shot this last one with support hand from the bench not using sand bags and rest.
Results are not impressive, but I'm satisfied, taking into consideration that
(a) it was my first time zeroing/shooting AR-15 rifle
(b) I was shooting with my "weak" eye (my cross-dominant eye was closed)
(c) I was experimenting with stock placement and support hand grip
Anyway, I happy that my groups are inside 3", I not always do this when shoot pistols from 7-10 yards.