I shoot Lapua brass for 6.5 x 47L. As others have mentioned, you can easily modify a "Lee Universal Decapping Pin" (they sell for about $5 each). I chucked the Lee decapping pin in my hand drill, and I used the file on my Leatherman multitool to turn the pin down to the required diameter. No caliper measurements necessary, just keep removing material and test it in a case flash hole until its fits easily.
I use this modified Lee decapping pin in a Frankford Arsenal Hand Deprimer tool. The Lee decapping pin fits perfectly in the FA depriming tool. I own two of these FA tools, one for large primer, one for small primer cases. Its a great tool, very quick (faster than on-press IMO), and no primer decapping debris mess on my bench or press.