Im using a peepsight on miy 357 max. Well the best Ive been able to do is a 4 inch group at 50 yards The front post is just too fat. It covers the whole target. Sooo what I did was I filed a v notch on the top of the front post & epoxied a piece of red fiber optic into the notch. The red dot I see thru the peep is half the width of the post. Shot it today 1 inch groups (average) a couple ragged holes. at 50 yards The best part is It looks like a factory job.

The pics dont show it real well , I used the fiber optic material off from a cobra bow sight pin(real cheap)
I still have to touch up the bluing
What I did was use a very thin cut off wheel On a rotozip & cut a notch in the top of post. Then 2 part epoxy 1/2 inch piece of fiber optic into notch.

