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Artillery: Lightweight Howitzer Joins the U.S. Army
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February 1, 2007: The U.S. Army has received its first M777A1 lightweight 155mm howitzers. Eventually, the army will receive 273 of these guns, at a cost of $1.7 million each. The British designed howitzer is also used by Canada, Britain and the U.S. Marine Corps (which is getting 377 of them). The army will use them in airborne and Stryker brigades. A five ton truck is used to tow the guns, but a special, 4.5 ton LWPM (Lightweight Prime Mover) is being built to do that as well. The five ton M777A1 is 40 percent lighter than the weapon it replaces, the M198. This is because the M777A1 makes extensive use of titanium, and new design techniques. It fires shells with a maximum range of 40 kilometers (using RAP, or rocket assisted projectile, ammo). A crew of five operates the gun, which can be ready to fire in under three minutes, and ready to move in under two minutes. The M777A1 is light enough to be moved (via a sling) by CH-53E and CH-47D helicopters. It's sustained rate of fire is two rounds a minute, with four rounds a minute for short periods. What will really make this gun useful is the new GPS guided Excalibur shell, which is entering service later this year. Otherwise, it fires unguided shells that land anywhere within a 200 meter circle. That's at 25 kilometers range. Accuracy gets worse at longer ranges. But not with the Excalibur shell, which falls within a ten meter circle (the middle of that circle being the "aim point") at any range. The Excalibur shell is essential, because ten 155mm shells (of any type, with their propellant and packaging) weigh about a ton. Ammo supply has always been a major problem with artillery, and Excalibur is the solution.

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doggtag       2/1/2007 8:28:59 AM
Saw that episode of Future Weapons that showed the Excalibur: the test shot they fired put the shell, they said, 2 yards from its intended point of impact.
 
6 feet.
 
Just under 2 meters.
 
Maybe they could make a HEAT or HEDP version for anti armor work (for use against those nations who like to use their tanks as stationary bunkers) if the miss distance is going to be under 10 feet.
 
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YelliChink       2/1/2007 10:37:22 AM
Sell Taiwan retired M198s!
 
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doggtag       2/1/2007 11:18:37 AM
No, YelliChink,
the US Army will dump all their "obsolete" and retired M198s onto the National Guard, just like they do with all their other worn out, broken down junk (the only new stuff we're even seeing now is because we're getting that Stryker brigade here in PA...and only those units in that brigade are getting anything new).
 
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HIPAR       2/1/2007 8:18:42 PM
Several years ago when I was testing a projectile tracking radar at Yuma proving grounds, a crew towed one of these British designed light weight guns past the test site.  They stopped briefly to talk with my test director and everyone suddenly had very amused looks on their faces.  Evidently they broke the gun .. they really enjoy breaking things at Yuma.  We used the M198 for the radar tracking tests.

---  CHAS

 
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Aaron.1815    circle of probable error   4/20/2007 11:06:50 AM
I'm new to this, but I was always taught that the circle of probable error was really an ellipse with the long axis in the direction of fire. Please correct me if I'm wrong.
 
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Sabre       4/20/2007 12:30:34 PM

I'm new to this, but I was always taught that the circle of probable error was really an ellipse with the long axis in the direction of fire. Please correct me if I'm wrong.

That is exactly right.  Lateral (deflection) error is minimal, call it... 10% of error range (depending).  So the major axis of that ellipse is 10 times longer than the minor axis.
 
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Jeff_F_F       4/21/2007 12:37:49 PM
My impression was that while there are both towed and SP arty units in both the Army and National Guard, most of the army's SP artillery is in the NG, and more towed units are regular Army. The rationalle seeming to be that you were more likely to need large amounts of SP arty in a long conflict, wheras the towed artillery is more deployable and also requires a higher level of training to use at maximum effectiveness.
 
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Jeff_F_F       4/21/2007 12:51:27 PM
In no way do NG units get dumped on. When the LCUs were comming out we (2/146FA 81st brigade WAARNG) had guys going to AIT who mentioned LCUs to their instructors and were told that they were lucky a lot of regular army units hadn't even received them yet. Granted we didn't receive the Paladin until 2002 but it wasn't like we were dumped on. The A6s hadn't been used at all, they'd been sitting in a warehouse for several years, but bureaucratic BS held things up. Too many layers of beauraucracy. Federal, Army, State, NG...
 
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HIPAR       4/22/2007 12:34:08 PM

I'm new to this, but I was always taught that the circle of probable error was really an ellipse with the long axis in the direction of fire. Please correct me if I'm wrong.

Actually,  the Circle of Probable Error (CEP) is a circle.  The fall of shot pattern is an ellipse with the longer axis in the range direction.  Muzzle velocity is the most difficult  precision error  to control in the overall system error budget.

If you compute the standard deviation of range errors and of deflection distributions with respect to the center of impacts, you can compute diameter of the CEP circle from these values.  The CEP circle is centered at the mean point of impact and bounds 50 percent of the impacts.

I wrote software that's used in projectile lot acceptance tests that plots the fall of shot and draws the CEP circle.  It's interesting to observe during actual firing testing how well the statistical processes develop.

---  CHAS

 
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neutralizer       4/23/2007 6:51:45 AM
For arty a CEP is really fiction, it is possible to combine the range and lateral PEs into a CEP, but whether its meaningful on the ground is another matter.  For unguided shells and range PE, the chance of 'all rounds falling within 200 m of the mpi at 25km' is also fiction.
 
I also note the claim that UK uses it, I hadn't heard that any decision on LIMAWS(G) had been anounced, M777 was one of the candidates.  Has an announcement been made?
 
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