Copperhead was never in service nor used by Canada, although some preparations were done to do so during op Cobra about 96 (or whatever that scheme was called) IIRC. It had an incredibly slow response time, and was affected by weather conditions.
Copperhead was not that reliable, and the warhead was designed to penetrate armour. It also required an observer to "paint' the target with a laser designator while the projectile was inbound, a daunting task when you consider all the laser warning devices available out there. But Excalibur was not designed to replace copperhead, originally it was a longer range and more accurate means of delivering DPICM, or SADARM, since then focus has been switched to a unitary warhead.
Potentially even an ordinary observer could request an Excalibur to engage a target, providing it fit the parameters of whichever attack guidance matrix is in use, this perhaps is one reason it complements, rather than replaces, aerial delivery munitions that require more specific skill sets to control. It also provides somewhat the same capability, albeit at a more limited range, that HIMARS or MRLS does, + the gun has the potential to deliver more conventional munitions (including non lethal) as well.
1st of all you're comparing what you've seen to what you haven't seen, a bit of a stretch, I have seen the results of a dud Excalibur round that has impacted into desert soil, there's not much left to work with. Besides that any normal HE round fuse that survives impact intact is highly unlikely to have come in at a steep angle, and Excalibur always does from high angle. If you look in Table G of any TFT and look at the steepest angle of fall and the terminal velocity when it does so, you will see why it is very likely those rounds you seen relatively intact came in shallow.
AUSSIE M198s TO BE UPGRADED TO FIRE "EXCALIBUR" ROUNDS.
Australia has requested from the United States the supply of 2,400 Modular Artillery Charge Systems(MACS),
250 M198 Block 1a-2 "Excalibur" artillery projectiles with base bleed units,
28 Portable Excalibur Fire Control Systems(PEFCS).
Training ammunition, containers, support equipment, spare and repair parts, publications and technical data, maintenance, personal training and training equipment.
US government and contractor representatives' engineering and technical support services, and other related elements of logistics support.
The proposed FMS sale, estimated cost US$40 million, is destined to enable an upgrade of a number of the 36 legacy M198 155mm pieces to fire higher precision guided munitions, on the basis such weapons may need to be deployed to Afghanistan at short notice, should the strategic situation on the ground suddenly changes.
Artillery coverage for the ADF is currently provided by the Dutch Forces.
Cannot Get Enough Excalibur
August 28, 2008: The U.S. Army has ordered another thousand Excalibur, 155mm, GPS guided artillery shells, at a cost of about $85,000 each. Australia ordered 250 of the shells earlier this year. American and Canadian troops have begun using the Excalibur shell in Afghanistan earlier this year. A year ago, American troops began using Excalibur in Iraq.
This was timely, because Islamic warriors tend to use civilians as human shields, and that means you have to be precise when you go after the bad guys. The Excalibur shell enabled the artillery to take care of these chores. A typical situation has enemy gunmen holding out in one building of a walled compound or village. In nearby buildings, there are women and children. While killing the enemy is good, killing the civilians can be a very bad thing. Smart bombs should be able to fix this, except that sometimes one of the smaller smart bombs, the 500 pounder, has too much bang (280 pounds of explosives).
A 155mm artillery shell should do the trick (only 20 pounds of explosives each), but at long range (20 kilometers or more), some of these shells will hit the civilians. That's because at that range, an unguided 155mm shell can land up to 100-200 meters from where you aimed it. This is where Excalibur comes in handy. The GPS guided Excalibur shell falls within a ten meter circle (the middle of that circle being the "aim point") no matter what the range.
After a year of use in Iraq, the troops find Excalibur invaluable for hitting just what you want to hit, and with a minimal amount of bang. Excalibur, being an artillery (which is controlled by the army) weapon, is easier to call in than a smart bomb (air force) attack. U.S. Army attack helicopters also have their Hellfire missiles, which provide a bit less bang than the Excalibur shell (and cost about the same). But while weather (especially sand storms) can interfere with helicopter operations, Excalibur is always ready to fire.
For most nations, the big drawback with Excalibur is cost. A "dumb" 155mm shell costs $300 or less, but when you take into account the civilian lives saved (and good will retained), it's a different story. Moreover, friendly troops can be closer to the target when Excalibur is used, meaning your infantry can get into the shelled target quicker, before any surviving enemy can get ready to shoot back.
The Excalibur shell is worth it in other ways. 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. With Excalibur, fewer 155mm shells have to be shipped thousands of miles, and looked after until they are used. One Excalibur shell can take out a target that would require 10-20 unguided shells.
Excalibur was developed in the United States, in cooperation with Swedish engineers, The Excalibur was originally supposed to cost under $50,000 each, and with more being produced, the per-shell price may eventually fall to the planned price. Currently, 150 Excaliburs are being produced each month, and the army wants to double that. Developing electronics and control systems that fit inside a 155mm diameter shell, and survive being fired out of a cannon, proved more difficult than expected. That's why a GPS guided smart bomb only costs about $30,000, while the first hundred or so Excaliburs cost more than twice as much.
Developing smart artillery shells is risky. The U.S. Navy recently cancelled a project to develop a similar 127mm shell, and is now looking into adopting the Excalibur technology for a GPS guided 127mm shell that works. Smart shells are a nice idea, but getting from here to there is a risky and expensive process.