Well, Echo, some aiming techniques are totally different: grenade launchers (like Mk19s) require an ability to lob at certain distances (and a realization that there's a minimum range) which you would never get with a rifle or handgun.
In support of Echo’s opinion, repairing firearms, repairing helicopters and repairing hydraulic mining equipment shares nothing in common except the a character with the “mechanic-1” skill can do all three.
As you are probably aware, real life soldiers train in a variety of weapons including assault rifles with grenade launchers. It does not take 2 years of training to teach a soldier to operate an assault rifle followed by another two years to teach him to use the grenade launcher. Even CT eventually recognized that someone could easily be trained in a broad variety of weapons and introduced the “combat rifleman” skill.
Echo apparently feels that many “skills” cover a broad range of experiences, while “weapon skills” seem to be disproportionately narrow in their scope. I find merit in that opinion (although I would probably not go so far as to combine all firearms into a single skill.
IN MY OPINION, to balance a skill like “rifle” with skills like “mechanical” or “pilot”, would require that the character knows everything that there is about that weapon, including repair of the weapon and reloading ammo. If “rifle” is to represent only the ability to aim and fire the weapon, then the skill needs to be broadened to include all related weapons – like “combat rifleman”.
I could see a case for three gun/laser/gauss weapon skills:
“one handed guns” (pistols, revolvers, gauss pistols, laser pistols, and any other pistol-like weapon);
“two handed guns” (shotgun, rifle ACR, auto rifle, laser rifle, carbine and any other rifle-like weapon);
“full auto guns” (SMG, MG, VRF Gauss guns, and any other weapon designed to “spray” an area).
While each of the weapons “aims and fires” a little different, a case could be made for basic familiarity with all of the weapons in the group and some overlap in how the weapon is used. Is shooting a rifle SO different from shooting a carbine that a Carbine marksman and a first time shooter would fire a Rifle with equal skill? That’s what CT Book 1 says.