I am guessing JIS is a Japanese standard.Wow, I never knew that.
What I do know is that there are various metric thread pitches as well as screw sizes.
I am not going to post info on something I don't know. For all I know Uberti builds guns with US standard thread pitch and size.
I love metric. Spent a lot of years with duplicated tools because of US and Metric standards.
Oh and by the way, there is a thing called JIS as well. Its metric but it ain't the same metric as real metric. Ask me now I know.