I, too have one of these sightpushers. The M&P Shield's can be particularly difficult to move the original sights on- actually broke a sightpusher (early version) on it... the tip broke off. He sent me a hardened version, and it's been fine. The guy gives great service. The Shields can be a BEAST to remove the sights from- I ended up having to cut the rear sight in half with a small cut-off disc in a Dremel... it just simply would NOT budge, even after blaster soakings, etc. Heard they install them with hydraulic presses at S&W- I'd believe it.
Wes