S&W 25's chambered for .45 Colt are famous for having too short a front sight on them. They did increase the front sights on the 25-7's and later guns, but not enough. I have to keep my 25-7 bottomed out on the rear sight, and I had to stone down the top of the rear sight on my 25-5 to get it to print in the bull even with it bottomed out. The 25's came with .126" rear sight lades, but you can either do what I did and stone the top down until it is printing in the black, or order a .106" rear blade kit from S&W.
The factory sights are setup to be usable with factory ammo, or handloads that are equivalent to the original load of a 250-255 grain lead bullet at approximately 800-850 fps. Anything else outside of a much lighter bullet at much higher velocity, and they won't adjust down far enough to center shots in the bullseye at 25 yards.