rondog,

Go to surplusrifle.com, and look at the subsections along the left side of the main page. You will see Type 99 Arisakaicon listed there. Pull it up; along the right side of that page there are articles about shooting the Type 99 that describe modifying .30-06 and 8MM Mauser brass to 7.7 Japanese. They also describe how to slug the bore, just in case you're interested in doing that.

I slugged mine just last week by using their tutorial; the barrel on mine mic'd at .313.