So, I thought I scored a super good Mosin...

SoreShoulder

July 21, 2013 12:31

Does anyone know what the diameter of a G.I. bore gauge's end is?

I am not trying to gauge a Mosin with one, I don't even have one.

I want to know how much of the height of the land has to erode away before the gauge can enter.

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  TRAP55

  July 21, 2013 16:56

  Are you trying to use a GI bore gauge on a Mosin?

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  SoreShoulder

  July 21, 2013 17:33

  quote:Originally posted by TRAP55
  Are you trying to use a GI bore gauge on a Mosin?
  no absolutely not.

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  beantownshootah

  July 21, 2013 20:22

  quote:>>Does anyone know what the diameter of a G.I. bore gauge's end is?
  
  No, but I don't know how relevant it is anyway.
  
  Standard US issue .30 cals (ie .308, 30-06) take .308 caliber bullets. Mosin Nagant takes a .312 caliber bullet
  
  quote:>>Can you gauge a throat by how far a rifle pushes a bullet into an empty case?
  
  I don't think that's going to give you an accurate measurement of anything.
  
  Lots of Mosins have bores like sewer pipes from neglect after shooting corrosive ammo. But there isn't always a good correlation between bore quality and accuracy. IE, sometimes nice looking barrels won't group for squat, and really awful looking ones can sometimes surprise you.
  
  Best way to test your gun is to actually shoot it, I think. Surplus Mosin ammo is available and cheap enough that this should be relatively practical.

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  ammo guy

  July 22, 2013 11:41

  If you mike bullets in 7.62X54R ammo they will run either .310-.311. The correct bore is .310 in the grooves for this and 7.62x39mm.

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  SoreShoulder

  July 22, 2013 16:30

  I don't even have a GI bore gauge. My point in asking is how much of any given bore has to wear away before it will let a wear gauge enter?
  
  Is an erosion about the size of a bullet, so the entire land would have to be washed away to the depth that the gauge could enter? (you couldn't tell by looking in the throat, because the grooves would erode too, from the white hot powder gas, and it would still look rifled)
  
  Or do the lands and grooves only get a little bigger before they're considered worn, partly because the edges round off a bit too?
  
  I could have asked if an m16 wear gauge is .2235, or smaller? because it would tell me how much of the total height of the land has to be gone where the gauge can enter.

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  TRAP55

  July 22, 2013 18:40

  Is your barrel stamped with a "D"?
  If it is, the throat of the rifle was opened up to allow use of the Finnish D166 round, it needed more free bore for the larger bullet ogive.

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  AmmoRat

  July 23, 2013 04:29

  Bore diameters vary and they made up for it with the bullets. Most of the surplus 7.62x54R ammunition has a hollowbase bullet to expand into the riflings.

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