Quoted:
For shooting at round bulls, try an aperture in the front sight. Only seems weird in your mind.
my Win 52 has a clear plastic front insert with a chamfered hole in the middle. there's no metal to block out the sight picture, but the angled edge of the hole is visible and great for round bulls... they just need to be the right size and at the right distance, but IIRC it works on the 50' smallbore bulls perfectly.
my Mossberg 146BA just got a new front sight that cost half what i paid for the whole gun, but now it has all 4 "posts" and the hood. there are two normal posts, one smaller and one wider, a post with a round dot on top and one with a larger ring with a hole in the middle.
they al work, it's just a matter of what you prefer, bod don't think some of the unusual inserts are useless just because they're not "normal" for other stuff.