I shot my accurised 1911 at one WIPL match (relaxed rules allow 45ACP) and was surprised when I beat some 32SWL shooters. Accuracy of 45ACP as a round is not a question. As to factory loads - yes there are winchester target loads sold at the same price as self-defence ammo, just a matter of being in a right store in a right time. I strongly recommend to roll up your sleeves and reload 45ACP, its the most rewarding part in terms of accuracy and cost. I would also recommend a visi to pistolsmith and tightening up your pistol, at least trigger work, slide fitting and bbl bush+chainlink. Most service-grade pistols simply weren't made for target shooting and need tune up. Well, if you are on the budget - at least replace barrel bush with something tighter, that thing alone may shrink your groups in half.
I guess what I was trying to say is that buying factory target loads on its own won't do the trick.