Don't see manny Arisaka posts so I wanted to jump in....
Glad you found your problem and that it was simply fixed.
I have a 6.5x50 Arisaka that was sporterized and rechambered to 6.5x55 swede.
I bought it from my 90 year old neighbor before he moved to the home

It shoots MOA at 100yds with my handrolled cartridges using 140 & 160 gr bullets and RE22.
I keep it at our ranch in Texas and use it for Hogs & Predators.
Its extremely effective on both...