I have 2 625-8's with SDM's. They are installed flush with the front (muzzle end) of the sight base and occupy all of the sight base but are not too long.The SDM sights are too long for the base on my 625-8. Check before you buy.
I have 2 625-8's with SDM's. They are installed flush with the front (muzzle end) of the sight base and occupy all of the sight base but are not too long.