You want an MA5 with a 60-round magazine? You don't actually have to build a new rifle for that. Hell, the MA5B 60-round magazine isn't that much bigger than the MA5C 32-round magazine. There's really no reason why a Marine shouldn't be able to

: At least in retrospect the
: MA5B and MA5C/D fill two distinct roles within infantry units. The former
: two are your standard service rifles with an "average"-sized
: magazine of 32 rounds. They're your M4A1 or AK-12 issued to absolutely
: everyone. The MA5B, in retrospect, is more of a squad automatic weapon
: with its high capacity magazine possibly in an attempt to standardize
: weapons at the squad-level.

I think you mean "The latter two" =P

And no. I don't think that's what the difference is. If the MA5B is a Squad Automatic Weapon, it's missing some key features. You'd think that it'd come with a bipod and a longer barrel than the MA5C, but that's not the case. And yes, I know that the official figures put the MA5B/C at 89 and 88 centimeters, respectively. That doesn't quite hold up.

Note: Above is the MA5C, below is the MA5B from H:CEA. The dimensional differences between the H:CE and H:CEA guns are trivial.

I tried to scale the two at what I think should be their actual sizes relative to each other. Any way you cut it, the MA5B is shorter and stubbier than the MA5C. The OAL of the C is nearly 10% greater than the B, and the B receiver is 15% taller than the C receiver.

If I had to write the lore difference between the MA5B and MA5C, the MA5C is the workhorse of the UNSC. It's the dirt-common assault rifle that gets handed out to every squaddie still scratching their newly-shorn scalp. It is good enough for any environment friendly enough for humans to have built a colony.

The MA5B is for everywhere else. It's not a glamorous spec ops toy, it's a gun built to withstand a very specific range of hostile environments, like the hard vacuum of outer space.

Oh, yes, I know. You can fire a gun in space because the propellant and the primer in a cartridge contains its own oxidizer. And if it's a particularly good gun, you can fire it twice. A very, very reliable gun might be able to empty most of its magazine before something critical malfunctions. You see, all guns require lubrication to some degree or another, and the liquid hydrocarbons we use tend to vaporize in hard vacuum. Vacuum welding will make the moving parts immobile, or at least they won't move very well. Furthermore, there's no convection cooling in space. Guns will heat up quicker and stay hot longer.

So, the MA5B has an ultra-low-friction coating baked onto the parts, a heavier barrel and bolt, and a massive heat sink for prolonged firefights on airless moons. This is a lot of weight for a trooper to carry around if they don't need it, so rifles the MA5C will remain general-issue for a long time.

If I absolutely had to explain why an MA5B fits 60 rounds into roughly the same volume that an MA5C fits 32, I'd retcon the MA5B to a 6mm cartridge. A proper one like the .256 British, not this underpowered 6.5mm Grendel or 6.8mm SPC fad.

: I wouldn't blame them trying to cut down on the number of weapons in a rifle
: squad. With the Marine TOE you're probably looking at an assortment of MA5
: rifle, M6 pistol, BR85 or M392 rifle, M7 submachine gun, M739 SAW, M45
: shotgun, and M41 rocket launcher. You could simplify the use of MA5, M7,
: and M739 completely with something like an MA5B.

Can't really see the shotgun getting much use.

: The M7 really should be
: reserved for vehicle and air crews, combat support/service support troops,
: and special operations troops.

Yes.

: The M739 is not much of an improvement on
: the MA5B with a mere 120% increase in magazine capacity. Widespread use of
: a rifle with a 60-rounder across the fireteam negates the SAW's rate of
: fire advantage. That's 4 shooters putting down 240 rounds at a time
: instead of 72.

Yup. You know what the Halo SAW should have been? This plus this. Something with a very large-capacity helical magazine and an incredible rate of fire that makes up for the slightly weaker punch of its intermediate-caliber round.