.217 or .218, what's your experience?

I have two slug capable PCPs (a .22/700 Impact MK2 and a .22/700 Panthera) and I'm considering setting up to swage my own slugs.

It's currently winter in Canada and too cold to test for the best diameter but because of delivery lead time I'd like to order the Corbin press and a set of dies to have them available for the outdoor shooting season.

I realize that every airgun and barrel may have it's own preferences but I'm trying to see if there is a general trend to .217 or .218 size in FX barrels.

Right now I'm thinking to buy .218 diameter dies and buy/make a sizing die if I find I need a smaller diameter slug.

I'd appreciate if you could post what barrels, slugs and diameters are working best for you.

Thanks!
 
First, did you slug your liners? do you have a micrometer? digital perhaps...
I don't have my numbers here with me, but you can do {{ zero to +5 microns}} to your groove in liner.
I cannot talk about slugs (yes I measured my liners but not shooting slugs), but I am resizing pellets for my liners (.22 and .25).
My background is mechanical and in my eyes the difference is huge between 0.217" (5.5118 mm) and 0.218" (5.5372 mm).
That is a 25 micron difference.
The Corbin sizer bushings are rough machine made - at least what people told me.
If that would be me - I would source to a machine shop with more precise dimensions and better surface finish.
 
On my Impact 700mm barrel the 0.216"s were not as accurate as the 0.217's (both NSA 24.8 gr). The 0.217's pushed through the barrel with about the right resistance and had MOA accuracy at 100 yds. I didn't even try pushing through a 0.218" because it would have been too tight. As bigHUN said, you should push a slug through the barrel to get a feel for the resistance.