Toolguy: They're a tapered hole and I'm not real good with the micrometer thingy but they're about .35 center to center, .25 at the top of the hole and .175 where they enter the bbl.
Seanc: They're not that bad really, I've shot Major 9 and safetyed behind many of them and I wouldn't put them in the same class. And I've chronographed them many times with the Ltd gun and I was really surprised at the small difference in velocity. Usually less than 25fps. Remember, I'm using lead bullets and I don't know if that matters. The lead is self cleaning in those hybrid holes, not so with a comp. You have to dig the lead out of a comp every 100 rounds. I'm just too cheap to buy jacketed bullets.