You know, Drill bits have a taper, they are wider at the business end and narrower at the end that goes in the Chuck. This is done to prevent the Drill getting stuck in the hole it just drilled. You may want to stop by a local machine shop, they often have scrap round stock too short to be practical to keep around and it's possible they'll let you have a piece. Hope this helps and getting to know a local machinist never hurts if you are into Guns. Greetings!
Thanks for your comment!
The biggest problem with using regular rod stock would be finding a piece of rod of the right diameter. You would probably need to have a piece of rod turned to the proper diameter. That would be ok if you have a lot of cases to do on a regular basis, but just for doing a few cases, it seems like an unnecessary expense.
I could probably get the local gunsmith to turn a rod for me for this, but I'd have to wait a while, hes got a lot of work most of the time.