With that in mind, I took a look at the CS arsenal and found a depressing lack of rail guns. The SAMAS flying power armor uses a rail gun. The Skelebots (think Terminator, but really, really dumb) use a couple of variations. That's it. The Skelebot models are listed as being used by troops in enhanced body armor, but they're really just used as oversized rifles - not an emplacement type weapon.
So, what to do? Glancing at the options and examining the role intended (use in a Heavy Weapons Squad), I think I'll have the CS port the C-40R (SAMAS rail gun) to a man-portable version. Or rather, I'm going to go back to the origin of the CS equipment: the NEMA equipment found in Chaos Earth. They have two man portable rail guns that seem to fit both squad and platoon level support roles.
The NEMA R-660 and R-670 were both rail guns intended to be fielded by two man human teams. The 660 was a lighter weapon, filling the role of M-60 or M-249. It had its own internal power source, negating the need to haul around the additional weight of a power pack. The 670 was a heavier weapon, analogous to the M-2. If the C-40R (SAMAS main weapon) is patterned off of the Silver Eagle's USA-40R, then there's no reason that the CS wouldn't have something similar to the 660 and 670. However, the CS aren't as advanced as NEMA was and have been reverse engineering their tech and using inferior materials. This translates to bulkier, heavier gear, accuracy degradation, and externalization of some features such as the power supply.
C-450R
This is a medium, all-purpose rail gun designed to be used by a two-man team or a single augmented user. The C-450R has a fair amount of recoil requiring it to be braced on a bi-pod for most users. Users with a PS of 22 or higher can use it without the bi-pod without penalty; users with a PS of 18-21 will take a -2 penalty to strike while users with less than an 18 PS will take a -5 penalty to strike.
The weapon is belt fed and takes the same ammunition as that used for the C-40R and C-200. Typically the weapon is deployed with C-200 style ammunition drums and belts as those are more man-portable than the nearly 200 lb drum used by the SAMAS.
Primary Purpose: Assault, Anti-personnel
Secondary Purpose: Defense, Light Anti-armor
Weight: Gun: 45 lbs, Ammunition: As C-200 and C-40R
Mega-Damage: A burst is 20 rounds and inflicts 4D6 MD. A single round deals 1d4 MD.
Rate of Fire: Each burst is one hand-to-hand attack.
Payload: As C-200 / C-40R