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Apr 27th, 2024
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Joined: May 2003
Posts: 339
Sidelock
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OP
Sidelock
Joined: May 2003
Posts: 339 |
Was asked today whether a browning B-78 can be rebarreled to .470 nitro.
Just how much metal is recommended in the threaded area.
He didn't have the barrel off yet, but the unthreaded shank by the breach was around the mid .8s in diameter.(threaded area .9?)
Thanks
Tom
Carbonation without fermentation is tyranny
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Joined: Nov 2006
Posts: 72
Sidelock
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Sidelock
Joined: Nov 2006
Posts: 72 |
Good place to start would be to compare the case size and max pressure of the .470 nitro round with the biggest round chambered by factory in the B-78. Also, should think about the bbl twist and bore size, ect.
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Joined: May 2003
Posts: 339
Sidelock
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OP
Sidelock
Joined: May 2003
Posts: 339 |
If the diameter is .900 and the base on the .470 is .572, that leaves about .160 on either side.
That doesn't seem like much.
I think that I have to look into those hoop stress equations that were in an earlier post on the board.
Tom
Carbonation without fermentation is tyranny
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Joined: Dec 2001
Posts: 6,993 Likes: 402
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 6,993 Likes: 402 |
Did you find it Tom?
I'm doing some similar reaserch, but my books I need are at work. Looking at putting a .450NE in a steve Earle falling block. Might have to modify the extractor. It seems a bit overly robust. It looks like as it is I have .138", a .544" baseon the .450 from the extractor cut which is .400" from center of bore. I'm think about thinning the extractor a bit. More reaserch needed.
Steve
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Joined: Feb 2002
Posts: 1,087 Likes: 1
Sidelock
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Sidelock
Joined: Feb 2002
Posts: 1,087 Likes: 1 |
The British NE cartridges have lower pressures than any of the large bore rifles based on the .375 NE Belted Magnum. A .470 will have lower pressure than a .458 Win Mag for example. Look at the well known German double rifles chambered for the .470. They have a surprisingly trim barrel profile at the breech.
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Joined: May 2003
Posts: 339
Sidelock
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OP
Sidelock
Joined: May 2003
Posts: 339 |
Originally the rifle buyer was looking at either the .470 Capstick or the .470 Nitro.
I'm not a fan of 0 taper cases, especially if all that you have is one shot. I knew that the Nitro worked at a lower pressure so it seemed to be the better choice. That is if it fits.
Tom
Carbonation without fermentation is tyranny
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Joined: Dec 2001
Posts: 6,993 Likes: 402
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 6,993 Likes: 402 |
I found my chart, one of my gunsmithing school handouts. It looks like I'll make just fine.
steve
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