Core diameter?

I think i'm going to go ahead and jump into powder coating and have one question. What size diameter do you guys prefer your boolits are before PCing? 1 or 2 thousands under bore size? At bore size? Other?

Thanks

Unless they are dropping rather oversized, just coat them as cast, and then size after baking.

Cast, coat, then size. As long as the bullets aren't unreasonably large to begin with you'll be fine.

If forced to choose i'd go with bore size or .001 over. The powder coat should add .001 to .002. I have a Lyman 358311 that drops bullets right at .358. I can add a coat of powder coat and not even worry about sizing.

In most cases Cast, Coat, and Size is good advise. However, you may want to consider what is going on here. Most boolit molds are designed for straight lead boolits not PC. Therefore, the boolit envelop and its interface to the barrel don't consider the extra 0.001 or 0.002 increase on full boolit envelop. Casting, coating, then sizing works well on the drive band area but it may not be so good further forward on the boolit. That extra thickness may cause early contact with the jump or bore regions of the barrel which can be a pressure issue. Check out the SAAMI for your cartridge, chamber and PC'd round to ensure fitment not just in the throat but the entire Chamber for all the COALs you plan to use. Really not a big deal until you blow one up.

use your normal boolit diameters.
you still have to have fitment to make the PC work effectively.
too small and you get leading.

if you been using 358 size to 358 after coating.

There is a low-tech method for checking fitment. Use a smooth solid color PC like HF Red. Make up about a half a dozen rounds without any primer or powder. Measure and record the COALS on each. Then cycle them trough your weapon. Examine the boolits for marks from feed ramps or chambers and check the COALS post cycle. No marks, Same COAL then you are good to go.