If you can't get the perfect fit on your 1861 stock Speedmaster bracelet, join the club. As far as stock bracelets go, it's not too bad. But man, trying to find the right fit is nearly impossible. Once again, Uncle to the rescue!
This version is not pin and collar (pre-1998), but the more modern version with screws (pictured).
One 1/2 link for the stock Speedmasterbracelet and accompanying screws.