Individual or Grouped
The damage you do is simply a function of the number of C4 you set off, whether you set them off individually or in groups.
Count
In his excellent analysis of BFBC2 damage, Den Kirkson analyzed the code and found that C4 does 290 damage at 0-1 meters, and then does a linear drop-off to zero damage at 8 meters. (A human without body armor in the game has 100 hit points, a tank has 1250.)
Kirkson doesn't document, and I don't know, exactly how much health an MCOM station has. But it takes 12 C4 to take out an MCOM station, so the health is somewhere in the neighborhood of 3400.
Which is a lot.
MCOM Collapse
Because of the MCOM's massive health, it's always better to take out a station indirectly by taking out the building when possible. This guide gives details on how many C4 it takes and where to place them on some of the Rush buildings. It takes much less C4 than taking out the MCOM directly.
Placement
It's fine to place your C4 within 1 meter of the MCOM, but be sure no indestructible obstructions will interfere with the blast radius.
Personally, I like putting them on the ceiling since enemies are least likely to look there when running in to disarm the MCOM.
Sequence
- Place the C4
- Arm the MCOM
- Run and hide
- Toss a motion sensor if you have one
- When enemies come to disarm the MCOM, detonate
I used to arm the MCOM before setting the C4. That was... um... a really bad idea. Gives people extra time to find you before you hide. Don't do that.
Loadout
People often think of C4 as a recon thing, but if you want to be a C4 thug you should really play assault and use one of the "all classes" weapons, which will let you pick C4 as your add-on. Your ammo crate gives you an unlimited supply of C4.
Regardless of which kit you play, if you take the explosives perk you'll be able to carry 6 C4 at once, enough to take out many buildings without re-arming.
Out of Bounds
One favorite tactic of... certain people... is to have a friend load up a UAV with C4 and pilot it right to the enemy's MCOM. Do this a couple of times and you can take out the station with no risk.
Except for the risk of getting cursed out, kicked, or even banned, because it's an incredibly lame tactic.
So don't do that.
Use Mines Instead
The engineer's mines have the advantage of staying around and active after his death. A recent poll in the BFBC2 forums shows support for this method.
C4 and AT mines with explosive spec equipped (x1.25) do the biggest blast damage - 362.5 points (soldier health is 100 points).
Tank shells with weapon upgrade spec (x1.25) do the most damage to tanks - 1093.75 points (tank health is 1250 points).
I don't know if any spec makes TOW shells stronger, but they do 900 damage to tanks by default (comparing to 875 from tank shells and 865 from C4/AT). So with 1.25 multiplier from a spec it would be the most powerful against tanks - 1125 points.
[Source]
Best Answer
The SPECACT parts were added together with a DLC, the SPECACT Assault, Engineer, Medic and Recon individual DLC's, as well as a bundle DLC that included all four.
The SPECACT DLC for a particular class gave you an extra weapon, basically a "SPECACT" version of one of the better weapons for that class, unlocked and ready for you to play with. It also gave you a "Kit" which is basically a different Camo-suite for you to wear.
On the menu, after installing the DLC, you can select either "Assault" or "Assault+" class to select which kit to use. The weapon is available to both classes, but not all game modes.
For the four classes, the weapons are:
The excellency pins are awared for reaching a kill count of 8 in any round with the specact weapons.
The efficiency pins are awarded for reaching a kill streak of 5 in any game round with the specact weapons.
The Insignias are awarded for reaching a total kill count across game rounds of 100 with the specact kits.
On Xbox 360 and PS3, there are achievements and trophies that are awared for getting all 3 awards (excellency pin, efficiency pin and insignia) for a particular class. On Xbox 360 these are worth 15GP apiece.