I see your

and raise you a

...
(Argh, serves me right to not read the whole text first... I was reading and commenting at the same time, so some of my comments were already addressed later in the text.)
[PLASMA CANNON]
X-Net://Pegasus.net/Armament/[Plasma Cannon]
The [plasma cannon] is a product of X-Corps research into the Aliens' plasma weaponry, and represents the first human-designed plasma weapon. Unlike other plasma weapons, the [plasma cannon] does not require separately manufactured clips. Instead, it uses Xenium directly from base storage as ammunition. The research team has done its work well - the [plasma cannon] easily outperforms every conventional weapon system in terms of damage output, and outranges them all save for the [Titan] missile.
"Plasma weapon" is a little vague; it is more accurately "aircraft plasma weapon".
Using Xenium "directly from base storage" can give the impression that the plasma cannon somehow can access base storage while it's off on a sortie somewhere. Also, the "as ammunition" part implies that Xenium is the
only thing in the ammunition. I know these two aren't the case, so maybe you could add something to underline the difference between plasma cannon ammo and handheld clip ammo? Perhaps something like, "Due to quantities of involved, reactants are
instead pumped directly into the weapon's storage tanks supplied to the weapon in a different manner," and mention Xenium as a reactant later in the text?
X-Corps scientists have improved the efficiency, muzzle velocity, and range compared to personnel plasma weapons, and added mechanisms to evenly mix reactants and fire plasma under the combat velocities and accelerations of our intercept craft. They have also increased the size of the device far above that of a handheld device, and redesigned the ammunition system to allow for clipless operation. While aircraft weight limitations dictate that only a finite amount of ammunition can be carried, its 99 shot capacity should be sufficient for any encounter.
If you like the idea about storage tanks I mentioned above, you could clarify the "clipless operation" part and change the "finite amount of ammunition can be carried" to some limitation of the storage tanks. If not, well, don't worry about it. 
The only other thing might be that "above that of a hand held device" could be "beyond that of a handheld device"... but that's more a proofreading thing.
The ammunition system has been totally refurbished, and is more complex than its predecessors. Adding ammunition is a three-step process, but is very simple and will be performed by the pilot instead of trained manufacturing or scientific personnel. The pilot will place the Xenium inside of a small chamber located on the side of the [plasma cannon], where an X-ray laser will fracture it into the normal powder. Then the pilot will add the mixture of shredded uranium, iron, and carbon to form the gel. The weapon will automatically test the gel for purity and place it in a holding tank if it passes. Adding heavy water is the last step, which is as simple as pouring it into a third opening, though it too is tested for purity to avoid contamination and possible plasma destabilization. Those pilots who are confident in their ability to live through the war are advised to follow proper procedures when handling the uranium.
Ahhhh, dag nab it. Please disregard my previous comments pertaining to "storage tanks".
Out of curiosity, why is the pilot doing this instead of maintenance crews?
"Normal"? Compared to what?
The last sentence sounds a bit strange... why are only confident pilots advised? Imho, it would make more sense if the sentence says, "Pilots who want to live through the war are advised..."
There something confusing in the paragraph, and I'm not quite sure how to explain it. I think it's because there is a change in the point of view and/or verb tense- "the pilot will place", "the pilot will add", "the weapon will... test", and then "Adding heavy water
is the last step [for the pilot]" and "it too
is tested". Maybe it's because sentence 2 refers to an existing process, while the explanation of the processes are in future tense...?
Argh, verb tenses aren't my strong suit.

I humbly suggest changing a lot of the future tense to present tense.
If, however, you keep the future tense, the paragraph might be something like (I've tried my best, but future tense is a bit confusing to me):
The ammunition system has been totally refurbished, and is more complex than its predecessors. Adding ammunition will be a three-step process, but will be very simple and will be performed by the pilot instead of trained manufacturing or scientific personnel. The pilot will place the Xenium inside of a small chamber located on the side of the [plasma cannon], where an X-ray laser will fracture it into the normal powder. Then the pilot will add the mixture of shredded uranium, iron, and carbon to form the gel which will be automatically tested for purity and placed in a holding tank if it passes. The pilot will add heavy water last by simply pouring it into a third opening, though it too will be tested for purity to avoid contamination and possible plasma destabilization. Those pilots who are confident in their ability to live through the war are advised to follow proper procedures when handling the uranium.
Present tense might be:
The ammunition system has been totally refurbished, and is more complex than its predecessors. Adding ammunition is a three-step process, but is very simple and will be performed by the pilot instead of trained manufacturing or scientific personnel. The pilot places Xenium inside of a small chamber located on the side of the [plasma cannon], where an X-ray laser will fracture it into the normal powder. Then the pilot adds a mixture of shredded uranium, iron, and carbon to form the gel which will be automatically tested for purity and placed in a holding tank if it passes. Adding heavy water is the last step, which is as simple as pouring it into a third opening, though it too will be tested for purity to avoid contamination and possible plasma destabilization. Those pilots who are confident in their ability to live through the war are advised to follow proper procedures when handling the uranium.
I've reworded some parts in the examples because I wasn't sure whether they were correct, and I wanted the example to be as correct as I could make them.
Aside from the above-mentioned alterations, the [plasma cannon] operates in the same manner as handheld plasma weapons, with the usual two-mixture ammunition and EM-triggered explosion. Eight magnetodynamic prongs collimate the burst. The Xenium is slowly consumed even after the shot leaves the barrel, but enough is present in each burst to maintain a coherent gravity bubble for 52km. This gravity bubble bursts upon striking the target, releasing the superheated contents. The plasma then spreads outward rapidly and consumes any materials in its wake. Although we expect UFOs to possess some partial immunity to plasma weaponry due to the heat-resistant nature of Alien Composites, the incredible power of the plasma cannon ensures that an impressive amount of damage will be inflicted. Against Alien Composites, the [plasma cannon] is 65x as effective as a [cannon], 10x as effective as a [Sidewinder], and 6.5x as effective as a [Titan], before considering differences in range or ammunition capacity.
It may be confusing whether Xenium is a part of the plasma, or separate from it. Maybe say, "The Xenium in the plasma burst is slowly consumed..."?
Just noticed that the verb "consume" is used in sentences 3 and 5- this may be too close together?
A scaled-down [plasma cannon] could conceivably be mounted on an XCAP. However, preliminary research indicates that a conventional, treaded XCAP, although able to support the weight of the equipment, would be difficult to maneuver and would run a high risk of being stuck in difficult terrain. Research into the principles of UFO construction may lead to new XCAP designs that can address this.
Perhaps be more specific about "UFO construction"- something like: "Research into UFOs and their ability to defy gravity may lead..."?
"At first I was skeptical, wondering how it could do all that much damage - it's not like it uses explosives or anything. After they tested it, the target was gone and part of the back wall had melted away. I never questioned the weapon after that."
Sorry, Kikanaide, if this post is messy. I had a really difficult time trying to explain why paragraph 3 felt weird, plus I had to go back and revise some of my previous comments.
Anyway, you have considerably improved the text. It flows a lot better, and though there are still some rough spots, the ideas well organized in each paragraph.
Crap, I had to edit the post because I messed up the quote tags.
...and a second time because code snippets ignore color tags.
...and a few more times for miscellaneous corrections and clarifications.
Edited by Astyanax, 14 July 2005 - 02:53 PM.