The idea of suppressive fire is to make the enemy take cover for fear of getting shot, keeping the enemy pinned down so that you can flank, call in armor or fire support to wipe them out, cover a retreat, or do whatever else requires keeping the enemy in one place. In game terms, this is how I feel it should work.
While wielding a semiautomatic or fully automatic weapon you may suppress a target that has full cover. Beginning suppression is a standard action, and you may suppress a five foot area with a semiautomatic weapon or a 10 foot area with a fully automatic weapon. You must fire 5 rounds with a semiautomatic weapon or 10 with a fully automatic when you begin suppression (full attacks are almost always standard actions in Voyager, as are some normally full round spells, as I want people to be able to fire and move a fair distance in one round, not stand around making five foot steps at the most), and you must fire the same amount of rounds every round thereafter. These rounds are fired at the cover the target is behind, not the target itself. If the target exposes itself in any way that downgrades the cover to partial cover or no cover at all, you make an immediate full attack against the target. The suppression ends if you fail to fire the required number of rounds or somehow fail to hit the cover.
If you successfully hit a target with 3/4 or 9/10 cover with a ranged attack (You need not be suppressing the target. This is a separate rule from suppression), you automatically threaten a critical hit. This is because a target with that much cover is likely only exposing the head or upper chest, so while that person is harder to hit with gunfire, any shot that does hit is very likely to have hit something vital.
Reloading a firearm is a move action unless otherwise specified in the weapon's description. The rapid reload feat reduces this to a free action.
Add your dexterity modifier to all firearm damage rolls, one and a half times your strength modifier to one handed melee attacks, and twice your strength modifier to two handed melee attacks.
Cycling the bolt on a bolt action weapon is a free action.
All attack actions, including full attacks, are standard actions. You may only take one attack action (a full attack counts as a single attack action) per turn.
Attaching a bayonet to a weapon is a move action. While the bayonet is attached you take a -2 penalty to all ranged attack rolls with the weapon due to the bayonet messing with the weapon's balance. A bayonet deals damage as a short sword, and is treated as a two handed melee attack.