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| The lands stand above the grooves. The groove diameter represents the bullets diameter and the tops of the lands represent the bore diameter.
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This is my rifle, there are many like it but this one is mine. My rifle is my best friend, it is my life.
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| | | Posts: 3171 | Location: SLC, Utah | Registered: 23 February 2007 | 
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| To put it another way - you bore out the barrel ,giving you the bore diameter.Then you cut grooves in the bore giving you the groove diameter or rifling !There are many types of rifling ;deep or shallow [microgroove], wide or narrow, sharp or rounded corners .There are different ways of making it ; cut ,button ,swaged etc. |
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| Ok so in other words the grooves are the rifling and the lands are the raised part in between the grooves that the bullet actually rides on. I understand now, i think, thanks alot everyone |
| | | Posts: 163 | Location: York Pa | Registered: 21 January 2005 |
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| The lands slice into the jacket of the bullet and provide the spin.
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This is my rifle, there are many like it but this one is mine. My rifle is my best friend, it is my life.
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| | | Posts: 3171 | Location: SLC, Utah | Registered: 23 February 2007 |
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| Some people dial in a barrel on the grooves, some on a spud that's held by the lands. |
| | | Posts: 9043 | Location: on the rock | Registered: 16 July 2005 |
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| In a .30-caliber rifle, the lands are .300 inches from each other, across the diameter of the bore. The bore has a major diameter of .308 inches. The lands cut into the jacket of the bullet by .004 inches. The bullet is .308 inches in diameter. The lands grip the jacket and cause the bullet to rotate on its long axis as it travels down the bore. The bore must be the same size as the bullet's diameter, or we will have a bullet that gets swaged as it goes down the barrel. This is not good; the barrel can get bulged, the bullet can get stuck, the barrel may even split open like a banana peel or like the rip in the hull of the Titanic. |
| | | Posts: 16534 | Location: Between my computer and the head... | Registered: 03 March 2008 |
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| quote: Originally posted by homebrewer:
In a .30-caliber rifle, the lands are .300 inches from each other, across the diameter of the bore. The bore has a major diameter of .308 inches. The lands cut into the jacket of the bullet by .004 inches. The bullet is .308 inches in diameter. The lands grip the jacket and cause the bullet to rotate on its long axis as it travels down the bore. The bore must be the same size as the bullet's diameter, or we will have a bullet that gets swaged as it goes down the barrel. This is not good; the barrel can get bulged, the bullet can get stuck, the barrel may even split open like a banana peel or like the rip in the hull of the Titanic.
Let's correct what you said. You are good up to "the bore must be the same size as the bullet". The bore is .300 in your example, how can it be the same size as the bullet. Bullet is groove diameter.... .308 The bore is .300 Groove diameter from groove to groove is .308 Groove depth is .004 |
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| And to further cloud the issue, the different barrel makers use different bore and groove diameters of the same caliber.
Jim Kobe
10841 Oxborough Ave So
Bloomington MN 55437
952.884.6031
Professional member American Custom Gunmakers Guild
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| quote: Originally posted by Jim Kobe:
And to further cloud the issue, the different barrel makers use different bore and groove diameters of the same caliber.
And bullets are not all the same diameter either.  Ray
Arizona Mountains
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| | | Posts: 1560 | Location: Arizona Mountains | Registered: 11 October 2004 |
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| quote: Let's correct what you said.
The overall bore in a finished .30-caliber barrel is .308 inches in diameter. The lands are .300 inches from each other, across the center of the bore. The lands are .004 inches high. The original bore starts out as .300 inches and is then rifled to where the major bore diameter is .308 inches. The bullet is .308 inches in diameter. We have a circle with in a circle, here. Not hard to understand... |
| | | Posts: 16534 | Location: Between my computer and the head... | Registered: 03 March 2008 |
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| You guys are arguing semantics. The bore diameter. is 300", the groove diameter is .308". Ray
Arizona Mountains
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| | | Posts: 1560 | Location: Arizona Mountains | Registered: 11 October 2004 |
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| Maybe it's the land diameter that is .300 and the groove diameter that is .308 inches. Whatever it is, I make sure I use the right bullets in the proper cases. Wouldn't want to put a .308 bullet into a .257 case... |
| | | Posts: 16534 | Location: Between my computer and the head... | Registered: 03 March 2008 |
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| Listen to Ray, he ain't an old fool.
Butch |
| | | Posts: 8964 | Location: Poetry, Texas | Registered: 28 November 2004 |
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| How 'bout them Yankees? |
| | | Posts: 16534 | Location: Between my computer and the head... | Registered: 03 March 2008 |
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