Iwo Jima

Discussions on WW2 in the Pacific and the Sino-Japanese War.
Post Reply
Carl Schwamberger
Host - Allied sections
Posts: 10056
Joined: 02 Sep 2006, 21:31
Location: USA

Re: Iwo Jima

#106

Post by Carl Schwamberger » 28 Jun 2013, 08:50

"wouldn't you have to have a direct hit on the opening"

In simplistic terms yes. I remember charts and tables for estimating this damage, have collected a few. The fast rule of thumb is if the projectile crater in 'average' soil covers the item it will damage it. ie: US 105mm howitzer projectile, 3kg explosive, must hit within a meter of a trench to have chance of collapsing the wall; A 155mm projectile, 7kg of HE about 1-5 meters. Thats surface bursts.

It changes when the projectile has a delay fuze. The energy from the expanding gas is transfered in a larger part to the soil, thus more against the target structure. So if you know you are attacking subsurface or hardened surface structure delay fuzes are preferable and perhaps AP or penetrating ammunition.

Still, even with 600kg+ HE charges we can be talking single digit distances from the target structure if well built.

Buried in the pages of the US Field artillery Journal are text and photos summarizing reports of test against a steel reinforced concrete bridge in the 1920s. Even the 240mm projectiles took suprisingly small bits off the bridge. A meter or two, the 105mm left scorch marks around chipped surface. With penetrating rounds you got holes completely through and a broken steel rebar or two. A single hit with a 20 or 35 cm projectile on a tunnel entry may leave it repairable in a few hours. For a target like that you need two or more damaging hits.

It is late and my notes are not here. but one more bit of trivia. 'Battleships' can do plunging fire. All projectiles follow a parabolic path modified by air resistance. It is a matter of having the appropriate range. For way to many reasons the navy gunners of 1945 did not always take advantage of this. Ok its time to go, next class we talk about skip or ricochet rounds and how to achieve a 40% rate in those.

OpanaPointer
Financial supporter
Posts: 5644
Joined: 16 May 2010, 15:12
Location: United States of America

Re: Iwo Jima

#107

Post by OpanaPointer » 28 Jun 2013, 09:14

The CEP, Circular Error Probability, for the BBs rounds when using plunging fire was way too large to take out the entrance to a tunnel, for example. To get plunging fire they'd have to be well away from the target and distance increases the CEP. Even when firing at something the size of a battleship most of the rounds missed.
Come visit our sites:
hyperwarHyperwar
World War II Resources

Bellum se ipsum alet, mostly Doritos.


User avatar
bronk7
Member
Posts: 396
Joined: 01 May 2013, 03:11

Re: Iwo Jima

#108

Post by bronk7 » 29 Jun 2013, 21:53

OpanaPointer wrote:The CEP, Circular Error Probability, for the BBs rounds when using plunging fire was way too large to take out the entrance to a tunnel, for example. To get plunging fire they'd have to be well away from the target and distance increases the CEP. Even when firing at something the size of a battleship most of the rounds missed.
sounds logical

OpanaPointer
Financial supporter
Posts: 5644
Joined: 16 May 2010, 15:12
Location: United States of America

Re: Iwo Jima

#109

Post by OpanaPointer » 29 Jun 2013, 22:30

The New Jersey's CEP was 50 ft. during the Vietnam era. So you could figure the safe zone was the blast radius plus 50 feet. The sane zone was a bit larger.
Come visit our sites:
hyperwarHyperwar
World War II Resources

Bellum se ipsum alet, mostly Doritos.

User avatar
bronk7
Member
Posts: 396
Joined: 01 May 2013, 03:11

Re: Iwo Jima

#110

Post by bronk7 » 06 Jul 2013, 16:25

OpanaPointer wrote:The New Jersey's CEP was 50 ft. during the Vietnam era. So you could figure the safe zone was the blast radius plus 50 feet. The sane zone was a bit larger.
I was in the USMC at Vieques Island [sic spell ] late 80s.......we were about 4000 yards away from impacts of USS Wisconsin[ I believe ] 16 inchers and they were MONSTROUS from that far away.....however, as we see in hsitory, it takes a close hit to kill well dug in troops....

OpanaPointer
Financial supporter
Posts: 5644
Joined: 16 May 2010, 15:12
Location: United States of America

Re: Iwo Jima

#111

Post by OpanaPointer » 06 Jul 2013, 18:31

bronk7 wrote:
OpanaPointer wrote:The New Jersey's CEP was 50 ft. during the Vietnam era. So you could figure the safe zone was the blast radius plus 50 feet. The sane zone was a bit larger.
I was in the USMC at Vieques Island [sic spell ] late 80s.......we were about 4000 yards away from impacts of USS Wisconsin[ I believe ] 16 inchers and they were MONSTROUS from that far away.....however, as we see in hsitory, it takes a close hit to kill well dug in troops....
During the Korean War the NK accused us of using nukes on them. Just a little old battleship round, ya'll. Like this one.

Image
Come visit our sites:
hyperwarHyperwar
World War II Resources

Bellum se ipsum alet, mostly Doritos.

User avatar
LWD
Member
Posts: 8618
Joined: 21 Sep 2005, 22:46
Location: Michigan

Re: Iwo Jima

#112

Post by LWD » 15 Jul 2013, 20:08


Delta Tank
Member
Posts: 2512
Joined: 16 Aug 2004, 02:51
Location: Pennsylvania

Re: Iwo Jima

#113

Post by Delta Tank » 21 Jul 2013, 21:04

OpanaPointer wrote:The New Jersey's CEP was 50 ft. during the Vietnam era. So you could figure the safe zone was the blast radius plus 50 feet. The sane zone was a bit larger.
At what range? When you consider that lethal fragments from a 8 inch howitzer go 1,000 meters, what would it be for a 16 inch gun??

Mike

Delta Tank
Member
Posts: 2512
Joined: 16 Aug 2004, 02:51
Location: Pennsylvania

Re: Iwo Jima

#114

Post by Delta Tank » 21 Jul 2013, 21:05

The marine sitting on that projectile. . .is he crazy?? Or has gone past the point of giving a shit?? Or both?? :D

Mike

OpanaPointer
Financial supporter
Posts: 5644
Joined: 16 May 2010, 15:12
Location: United States of America

Re: Iwo Jima

#115

Post by OpanaPointer » 22 Jul 2013, 00:43

Delta Tank wrote:
OpanaPointer wrote:The New Jersey's CEP was 50 ft. during the Vietnam era. So you could figure the safe zone was the blast radius plus 50 feet. The sane zone was a bit larger.
At what range? When you consider that lethal fragments from a 8 inch howitzer go 1,000 meters, what would it be for a 16 inch gun??

Mike
The range I remember was 16 miles for that figure. The blast radius would depend on the round. I'd have to dive deep for that information and my big box is in the shop.
Come visit our sites:
hyperwarHyperwar
World War II Resources

Bellum se ipsum alet, mostly Doritos.

OpanaPointer
Financial supporter
Posts: 5644
Joined: 16 May 2010, 15:12
Location: United States of America

Re: Iwo Jima

#116

Post by OpanaPointer » 22 Jul 2013, 00:44

Delta Tank wrote:The marine sitting on that projectile. . .is he crazy?? Or has gone past the point of giving a shit?? Or both?? :D

Mike
Just a smoking cup of macho, that's all. 8-)
Come visit our sites:
hyperwarHyperwar
World War II Resources

Bellum se ipsum alet, mostly Doritos.

Delta Tank
Member
Posts: 2512
Joined: 16 Aug 2004, 02:51
Location: Pennsylvania

Re: Iwo Jima

#117

Post by Delta Tank » 23 Jul 2013, 19:09

Carl,

What was the CEP on the 155mm M109A1 Howitzer? Could you break the CEP into Range and Deflection Probable Error? I do not recall any conversations on CEP, we always talked about Range and Deflection Probable Error.

Mike

glenn239
Member
Posts: 5862
Joined: 29 Apr 2005, 02:20
Location: Ontario, Canada

Re: Iwo Jima

#118

Post by glenn239 » 24 Jul 2013, 18:43

The New Jersey's CEP was 50 ft. during the Vietnam era. So you could figure the safe zone was the blast radius plus 50 feet. The sane zone was a bit larger.
50 feet? Wow, that’s good. On Hyperwar you have a USMC doctrine manual from pre-WW2 giving 8” cruiser gunfire a spread of, I think it was, about 300 yards. For 50 feet, I’m thinking the ship has to be pretty close in.
At what range? When you consider that lethal fragments from a 8 inch howitzer go 1,000 meters, what would it be for a 16 inch gun??
In the Technical Missions to Japan info, if you look hard enough you can find a table that gives the effective AA radius of Japanese HE shells up to 18.1”. That's a rough guide on how far splinters travel (but doesn’t give you information on the density of splinters as you move out from the blast).

User avatar
bronk7
Member
Posts: 396
Joined: 01 May 2013, 03:11

Re: Iwo Jima

#119

Post by bronk7 » 24 Jul 2013, 18:50

isn't that spread from all the 8 inchers at once?

OpanaPointer
Financial supporter
Posts: 5644
Joined: 16 May 2010, 15:12
Location: United States of America

Re: Iwo Jima

#120

Post by OpanaPointer » 24 Jul 2013, 21:00

bronk7 wrote:isn't that spread from all the 8 inchers at once?
I'm pretty sure that's how it went, but I haven't seen the page in question lately.
Come visit our sites:
hyperwarHyperwar
World War II Resources

Bellum se ipsum alet, mostly Doritos.

Post Reply

Return to “WW2 in the Pacific & Asia”