japan is <1J for legality there. modifying it there by yourself would be breaking their firearms laws. And even if you did have it modified, you'd have to get it tested here.
Is it a rare gun? TMs are dirt cheap there, is it really worth going through the trouble to get it modded to meet standards here for import and then having to go through the trouble of getting it tested when it hits the border and still potentially getting it seized?
I futz with V2s, V3s and V6s. I could be wrong... but probably, most likely not, as far as I know.