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Okay, back to the quest!! I have spent the past four weeks reading completely all of the books I purchased. Vic Venters' Gun Craft; Ellis Brown's Building Double Rifles...; Graeme Wright's Shooting..British Double..; and Steven Hughes' Double Guns..Custom Gunsmithing. I also bought three new ammunition books with good readable text and reliable data (I thought..??). Ammo Ency.-3rd Ed.; Ammo and Ballistics-4th Ed. and Cartridges of the World-12th Ed.. I was completely surprised to see the ammunition books had significant differences when referring to the .470 NE and the .500 NE. I will highlight a couple---On page 400 Cart. of the World shows the rim diam. of the .470 NE at .646 then further back on page 556 it shows it at .655. On the same pages it shows the rim thickness at .035 then later on at .037...???? Ammo and Ballistics 4 shows rim diam. at .655 and rim thickness at .040. Ammo Ency. pretty much agrees with A&B 4. On the .500 NE Cart. of the World shows the rim diam. at .660 on page 400 and again on pg. 558. A&B 4 shows rim diam at .655 and thickness at .040. Ammo Ency. carries their dimensions out four decimal places and they vary a little from the others.....So which of the books is correct?? I am confused..

Since A&B 4 and Ammo Ency. are the closest to each other I will assume that they are the closest to the truth. Just can't imagine that much difference between the books...Have these cartridges changed dimension over the years?? Could older factory cartridges have different dimensions?? I would hate to cut chambers for a rim thickness of .040 only to find that manufacturer X or Y has a rim thickness of .035!! Five thousandths excess headspace could be problematic!!!

If in fact the rim diameters of the .470 and .500 by current specs are the same------Ammo Ency. shows the average max pressure of the .470 NE at 39,200 (PSI) and the .500 NE at 32,000 (PSI)....this would seem to indicate that the breech thrust of the .500 would be significantly..?? less than the .470. Do you find this to be true?? This of course would require you to believe the book specs....I realize that SAAMI and CIP control the specs, but what do the manufacturers do in reality?? Do they load these particular cartridges to those average pressure specs or to a "standard" velocity for a specific projectile. This would indicate the possibility (probability) that the pressures could change by manufacturer depending on powders and projectiles used (which makes sense because I know various manufacturers of other cartridges use different propellants and achieve different ballistic results). So, maybe I have answered my own question, but....In any case, have you found these pressure specs to be at least somewhat reliable??

Lastly, I have inspected the two double guns that I own and find that they are not in as good a shape as I thought (hoped..). I have taken pictures and will post some next time for each of the guns along with some questions..!!

I want to thank everyone for your patience...I admit to being a newbie with double rifles, but I learn fast!

Thanks again!

Howard

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...Howard...

Have tool will travel..

If you are not part of the solution,....You are part of the problem!

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