You asked for our 2 cents , so I'm going to give you my 5 cent opinion . Why do you want to throw away $380 dollars on some novelty gun that you cant use for anything once your friends go back to Japan ? Total waste of money . Buy something that YOU can use for hunting in the future .
I think you guys would have more fun shooting an inexpensive bolt action rifle on targets for accuracy rather that building a useless gun . Get a smaller caliber like 243 or 7mm-08 because they are not used to recoil .