hello I bought a old mauser with a custom stock it still bears the military barell. It has been chamber reamed to 30 06. it is a 1909 argentinne mfg by dwm berlin germany. The bullet diam of the barell is .311 not .308 as it should be with 30 06. It is of poor accuracy capable of diner plate groups at 75 yds. can I neck size seating 8mm bullets in 30 06 brass so theres a good seat in the grooves by the bullet or will there be pressure issues? also is the 1909 a large ring? and can it substain 30 06 pressures? I hear the receivers need heat treating some say yes some no. I appreciate your responses very much and I know alot dont take kindly to a butchered mauser. But for some reason at $75 it said take me home you wont be sorry..8mm/06 loads?????
thank you

Do NOT use 8mm Mauser bullets in your Argentine Mauser. Your Argie bore diameter will range from 0.308 to 0.312. The 8mm Mauser bullets are 0.323 diameter. You will effectively put a large cork ina small hole and the pressure will not escape fast enough so you will most likely blow up your Argie. Try the heavy bullets intended for either .303 British (0.311 diameter) or light bullets intended for 7.62 x 39 (0.311 diameter). Good luck and be careful. Charles.  

The Model 1909 is a large ring Mauser.
The DWM produced rifles were very likely the finest quality Mauser ever built, and were the only military model to have all the commercial features, like the pear-shaped bolt knob, and the commercial-type hinged floorplate.

Unless the rifle has been WELL used, and shows signs of head space problems, or shows heavy seating of the locking lugs, they are quite safe with the 30-06 and don't require re-heat treating.