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Posted by squeakie
on Wednesday, November 5, 2008 1:12 PM
 subfixer wrote: | | squeakie wrote: | | ddp59 wrote: | |
went to the link provided, and I really gotta question the 35 mile hits. To be exact I think who ever figured it flunked Algebra II. Even if using the 260lb. round you ain't get there, and ballistics say it would have to be the 335lb. round to retain the maximum amount of energy at extreme ranges. A 175 gun setting at 1500 ft above the target shooting a zone three charge and a 147lb. round will do about 25 miles (some say 27 miles). An eight inch howitzer from that period was good for about 9 to 9 1/2 miles using a charge similar in size to what is shown (so maybe the Navy was using two of them?). Taking into fact that barrel they were using was about 2 1/2 times longer, and the howitzer was using the standard 204 lb. projo it just don't add up at 2600 fps. The 175 gun round has far a better ballistic coefficent, and is a very similar design to what the 1000 yard target shooters use in rifles, but of corse bigger (they figure their spec of a 2668 fps velocity), and left at 3300+ fps. Maybe 25 miles max. When the Battleship New Jersey shot for us they were doing about 23 miles, and that was close to all they had. gary |
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This was special ammo, this is from the link: 5) In the late 1960s the "Gunfighter" program at Indian Head Naval Ordnance Station developed Long Range Bombardment Ammunition (LRBA) projectiles. These were Arrow Shells with a body diameter of 4.125" (10.4 cm) and a fin diameter of 5.0" (12.7 cm) which were sized to be fired from 8" (20.3 cm) guns by using a sabot and obturator system. Tests with these in 1968 showed maximum ranges of 72,000 yards (66,000 m). The burster in these shells was PBX-w-106, a castable explosive. Sabot weighed 17.6 lbs. (8.0 kg) and was discarded as the projectile left the muzzle. After a test firing off Okinawa of three inert-loaded shells, USS St. Paul (CA-73) in 1970 conducted a two day bombardment mission against Viet Cong positions at ranges up to 70,000 yards (64,000 m). At the time, St. Paul was the only 8" gunned cruiser still in active service. |
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I don't know who did the equations, but the numbers still are not there. I spent two months doing FDC, and I can't see it. Maybe 35 kilometers or with a RAP round. Guess I better dig out my math books to see just what it takes to push a 17.6 pound dart 35 miles. The hottest gunpowder used by the western allies in the sixties and seventies was what they used in a 175 gun. And this was a charge (zone three) that was 5'7" long and over a foot in diameter with a special priming tube right up thru the middle to get a complete powder burn. If they used that same powder in the 8" guns on that cruiser, it would have been about equal to two of the shown charges. But that's not the problem. It's the round itself. Lighter(in weight) rounds tend to dissapate the energy needed to move them thru the air ( a basic inverse proportion equation), and this is why very long distance bullets are heavy and very long. For that SABOT to be effective I'd guess it tobe at least six feet long if not closer to eight feet (the longer rounds tend to have a better ballistic coefficent assuming that they are of course shaped right). The 7" diamter round in the 175 had a B/C of nearly .500, where the average round was below a .300. It also had a very pronounced "boattail" (over twice as much as a 155 round), and used a "secant ogive" in front. If they'd used a conventional bullet design the round would have lost about 30% in range. I'm still a doubting Thomas gary
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