How close to bore size you make your bullets depends on the hardness of the lead. Once I bought some Dardas 45 200 grain bullets to shoot them and others from my ransom rest through my Les Baer to find the most accurate bullet available commercially. I accidentally bought a hundred of them sized .451. I thought no big deal and I will just use them to settle the ransom rest before testing what I figured would be the best. While shooting 10 rounds I came up with a group around two inches at 50 yards. I and my friends were amazed and said I should buy some .452's and some .453 so I did and when testing them, the .452's were worse with the 453's being even worse around 7 or 8 inches. This amazed me because my best groups with cast bullets were sized at .452 however the BHN on the Dardas measured around 17 and my cast measured 9. I assume the hard bullets did not like being swaged down but the soft ones did not mind. I also tried some of my soft bullets sized at .451 and they shot around 4 inches. Don't know for sure the reasons for all this but is something to think about and try if you don't have good results in what you are doing. All kinds of reasons for we don't know what.