Hornady OAL gauge/ How to Thread Modified Cases?

[Tactical30]

I had recently got into reloading and realized that a Hornady OAL tool and Comparator are one of your best friends.
The problem is Hornady does not make a modified case for the
6.5 Grendel round. What size drill and tap do you use to get the correct threading to fit the OAL gauge?

Thanks

 

[ZY100]

Re: Hornady OAL gauge/ How to Thread Modified Cases?

5/16-32 tap and 19/64 drill. Yes, odd sizes, but you can find them online--probably not at true value or Home Depot...

ZY