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Shooting & Reloading - Mausers, Big Bores and others >> Big Bore Rifles
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docEE
.224 member


Reged: 06/11/03
Posts: 28
Loc: Minnesota, USA
chamber pressures for NE's?
      #5607 - 12/12/03 07:28 AM

I realize this is a pretty basic question, but find I do not have the answers in any of my books. What are the chamber pressures of the various nitro express cartridges? Specifically the 470 NE and the 450 3-1/4", but I am curious about others as well. Is it 40,000 PSI? Do this old English cartridges have SAAMI pressure specifications now?

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DUGABOY1
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Reged: 02/02/03
Posts: 1340
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Re: chamber pressures for NE's? [Re: docEE]
      #5609 - 12/12/03 08:33 AM

docEE, A good place to see most of the factory pressures for NE rounds is in Graeme Wright's book " SHOOTING THE BRITISH DOUBLE RIFLE". These are reprints of the old ammo makers. I doubt you will find any of the old true NE rounds made to be used in doubles that will generate 40,000 psi chamber pressure. The highest I find is the 450NE 3.25" 17 Emperial tons X 2240 (Emp long ton) = 38080 psi chamber pressure.

The 470 is listed at 14.0 E-tons x 2240= 31360 psi. There are some cartridges that are chambered in double rifle that generate more pressure, but those are generally small diameter rounds like 30-06, and 7x57R that generate around 40,000 psi, but they have plenty of steel wrapped around the chambers, and are not a problem because of pressure. Rounds like the 375 H&H, belted rimless, and 416 Rigby that cause the problems, with a combination of pressure, and the RIMLESS configuration.

The S/S double rifle is basicly a 30,000, to 35,000 psi system, that works best with a flanged cartridge, of low chamber pressure! As has been proven by the last 100 years of use, nothing more is needed, no matter what the gun rags say!


--------------------
..........Mac >>>===(x)===>
DUGABOY1, and MacD37 founding member of DRSS www.doublerifleshooterssociety.com
"If I die today, I have had a life well spent, for I've been to see the Elephant, and smelled the smoke of Africa!"

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docEE
.224 member


Reged: 06/11/03
Posts: 28
Loc: Minnesota, USA
Re: chamber pressures for NE's? [Re: DUGABOY1]
      #5626 - 13/12/03 03:14 AM

I was wanting to compare those two cartridges to get an idea of how trim a 450 NE 3-1/4" barrel could be. For an identical chamber pressure, and with the same steel type, the outside diameters of the barrel over the chambers should be proportional to the cartridge diameter. That is to say, a cartridge with a case only 90% as fat as another could have a barrel only 90% the diameter and still handle the pressure. From what you say, however, the 450NE has higher chamber pressures, so you could NOT make the barrels proportionally trimmer and still handle the pressures. My previous reading had suggested that this round has historically had the option of trimmer barrels. It would seem this is at the risk of a lower safety margin.

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DUGABOY1
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Reged: 02/02/03
Posts: 1340
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Re: chamber pressures for NE's? [Re: docEE]
      #5627 - 13/12/03 06:45 AM

The reason this round was touted to be used in lighter rifles, is because it came out as an alternative to the old things like 577NE, and Guage guns, which were built in the range of 15, to 20 lbs.

The 470NE and all the .450s were made in the same action size, makeing the outside diameter of the chamber areas the same. That has not set asside safety because of the higher pressure of the 450NE 3.25", because the 470NE is only in existance because the .450 diameter was outlawed in 1909, in India, and the Sudan. For all practicle purposes, when the bullet from either of them hits a buffalo they are the same! The 470NE will not do anything the 450NE 3.25" or anyt of the 450NEs will not do as well! The 38080 psi of the 450NE 3.25" is not high at all. If you want a .450 that is very low in chamber pressure that is just as good as either of the ones being discussed, then go to the 450#2 NE, it only developes 13.0 Emp tons, or 29,120 psi chamber pressure, and will do anything the others will do, in the same weight rifle!


--------------------
..........Mac >>>===(x)===>
DUGABOY1, and MacD37 founding member of DRSS www.doublerifleshooterssociety.com
"If I die today, I have had a life well spent, for I've been to see the Elephant, and smelled the smoke of Africa!"

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