I recently requested information from Davidson Guns regarding the actual bore diameter of the Mini Thirty and Model 77 rifles of this caliber. I'm considering reloading, and had heard different stories on the true bore size. The following was the reply I received today. I thought others might find it interesting as well:
Dear Mr. Phelps,
Thank you for your inquiry at www.GalleryofGuns.com
! Ruger's groove
diameter for the 7.62X39 caliber cartridge for either the Mini-30 or model
77's is .3100 - .3115 according to their engineering dedpartment. This is a
compromise diameter designed to shoot either the .308 or .313 diameter ammo
that is available. A .311 diameter bullet would be my choice for handloading
applications if available.
I hope this helps!
Rebecca L. Gridley