I think your problem could be with the bullets. Your loads are similar to what I have been using, but I had 5 gr of Unique. I have been using the Berry's plated RN bullets for some time and found that in a couple of my 9 MM pistols the accuracy was quite poor. I recently ordered 1000 of the Berry's flat nose bullets and they are WAY more accurate in the two pistols that did not like the round nose bullets. I think if you experiment with some different loads you will probably find something your 1911 likes.