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Bullet vs bore diameters

MVPMVP Member Posts: 25,074
I have heard about Ruger Mini 30 being hammer forged with their .308 rifle barrel mandrels and how it is one of the causes for there to be a lacking in accuracy because of the 311 diameter of the 762x39 bullet.
Forcing a .311 bullet down a .308 bore.
What got me thinking about this is
I measued the bore on an old 9.3x72 rifle and it is measuring .358 and available bullet diameter is .366
This doesn't seem right to me.
What am I missing, will there be excessive pressure or is it going to be ok to handload the .366 bullet and fire it down a .358 bore?

Comments

  • Hawk CarseHawk Carse Member Posts: 4,319 ✭✭✭
    edited November -1
    Bore or groove diameter?

    If the groove diameter is .358" you have a 9x72R which is not nearly as common as the 9.3x72R. I would not remotely consider cramming a .366" bullet down a .358" barrel.
  • MVPMVP Member Posts: 25,074
    edited November -1
    quote:Originally posted by Hawk Carse
    Bore or groove diameter?

    If the groove diameter is .358" you have a 9x72R which is not nearly as common as the 9.3x72R. I would not remotely consider cramming a .366" bullet down a .358" barrel.

    Thanks for the correction.
    It is the groove diameter.
  • MVPMVP Member Posts: 25,074
    edited November -1
    do you have any information on the 9x72R or can you point me in that direction internet or otherwise?
  • Hawk CarseHawk Carse Member Posts: 4,319 ✭✭✭
    edited November -1
    The last time the subject came up, I found a mention or two of it but did not save the source since discussion dropped off.

    Huntington's lists special order RCBS dies for it, that is all I can find today.
    http://www.huntingtons.com/dies_specialorder.html
  • sandwarriorsandwarrior Member Posts: 5,453 ✭✭✭
    edited November -1
    MVP,

    Seems that it would be a 9mm not a 9.3. Anyhow for older cartridges these guys have a ton of stuff: http://www.buffaloarms.com/ they didn't have any 9x72R that I could see but may know where to find it.

    As for the mini-30, I think the inaccuracy starts with the manufacturing process being made to handle so many different type rounds and that, that type action is built using tolerances more attuned to functioning than to fine accuracy.

    -good luck
  • iwannausernameiwannausername Member Posts: 7,131
    edited November -1
    IIRC when the mini30 was first introduced G&A (or other magazine) stated that Ruger uses a tapered barrel - 311 near the chamber, tapering to 308...
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