One of the determining factors of bushing size is the OD of your case neck with a bullet seated measured over the pressure ring of the bullet. You will find that a bushing that gives .0025 to .003 difference between sized and loaded neck diameters will work fine. Wilson bushings seem to have the advantage of being able to produce .0005 more sizing than their nominal size by flipping them. Other powders such as the LTs will be fine with .001 less neck tension. Loaded round neck clearance in the chamber in the range of .002 to .003 will work well. I have worked with half that, but much better shooters than I tell me that more gives a more consistent bullet release, and that that shows up most noticeably at 200. So, you should start out by carefully measuring the largest diameter of your bullet with a micrometer (not a caliper) that reads to .0001", add your total clearance to that, subtract the total from your chamber neck diameter to get 2X your required neck clearance, and divide that number in half to get the thickness that you will turn your necks to. I like to polish freshly turned necks, under power, with 0000 steel wool, because it tends to level off the turning pattern on the OD to a condition similar to the result of a few firings. I do this before measuring thickness with a neck mic. Before I had a neck micrometer, I seated a bullet that I had carefully measured, measured the diameter of the loaded neck over the largest diameter of the bullet, subtracted the bullet diameter and halved that result to determine the necks thickness. Once you have the loaded neck OD that you will be using, you can do the math to come up with a range of bushing sizes to try. I find that for 133, depending on bullet diameter and neck thickness I typically am working with .257 and .256 bushings.
