The last few weeks have been about changes to the Swords and Wizardry combat mechanic. Here’s how it all ties together in my Chimera/S&W mash-up (which I’m calling, in honour of G. MacKenzie, Lich Lord) “Spear & Spell.”
I’m defaulting to Moldvay for initiative. While I like individual initiative, side-based initiative seems to be a better fit here, possibly faster, and it still lets you employ strategery.  I figure 1d6 per side, with each round broken into the following phases:
Astute readers will note that I’ve added a couple more phases, but I kept the “M”s, which stands for things like Mandatory. And Moldvay. Each phase is resolved in initiative order before moving to the next (i.e., side A moves, then side B, then side A does miscellaneous stuff, then side B, etc.).
Another nod to Moldvay, whose Basic D&D included a 2d6 morale roll, which was compared to a monster’s morale stat.
Interestingly, Moldvay’s Encounter Reaction table also used 2d6, and I’ve always had this notion of combining the two, essentially defining morale as a Reaction roll made during a fight. Since S&W monsters don’t include a morale stat, this is the perfect opportunity:
Die Roll (2d6)
Before a fight
During a fight
Fight to the death
Hostile, likely attack
Cautious, monster confused
Non-hostile, monster leaves
A GM should check for morale reactions when the encounter first occurs. Once fighting starts, check after check for morale at the beginning of each round and apply modifiers for taking the first casualty wound, when the number of allies falls below 50%, and when the leader is eliminated from the fight (This update made on 12 Oct.; as a result, I'll include these modifiers in another post - EDS). The Charisma of the party leader may modify the morale roll at the GM’s discretion.
A slight deviation from the S&W standard: A character’s base movement indicates the number of tabletop inches he can move in a combat round. Each inch is worth 10’ inside or 10 yards outside.
For now, my working model includes the Movement Die used in Chimera, which is rolled when a character runs or creeps. So, you might have a movement rate of 9±1d6, meaning that you can walk 9” per round (i.e., 90’ inside or 90 yards outside), run 10-15” per round or creep 3-8” per round.
Any movement is resolved during this phase. Running or creeping takes the full round, but if you walk at your normal speed, you can still act during one of the remaining phases (Miscellaneous, Missile, Magic, or Melee, below).
I also like the idea of resolving backstab attacks during this phase. I mean, you watch movies—does anyone ever get backstabbed after the action starts?
This is a catch-all for non-attack and non-magic actions, like picking a lock, breaking down a door, pushing a boulder over a cliff, wriggling free of a spider web, trying to figure out the mechanism that controls the platform suspended by a chain over a fiery pit to Hell, etc.
These actions may or may not actually require a skill roll, and they may be complicated (or impossible) if there’s a foe in melee range.
Any non-magical ranged attack—firing a bow, shooting your radium pistol, or throwing a rock. Roll 1d20 and add your class-based to-hit bonus; if the result equals or exceeds your target’s movement rate, the attack hits.
A few tweaks to what S&W says:
First, adjust for scale by dividing the weapon’s range by 10 (round fractions down). The result is the weapon’s range in tabletop inches. For example, a long bow’s range is 70 feet in the S&W rules; this is 7” on the tabletop, which means 70’ indoors and 70 yards outside.
Second, range should be interpreted as “effective range,” meaning that a shot fired at a target within range is unmodified. The to-hit penalty for longer shots is the target’s distance divided by weapon range (round fractions down). So I have a long bow and my target is 6” away—no penalty. At 7” the penalty is -1, at 10” the penalty is -1, at 14” the penalty is -2, and so on. Not sure about maximum range, but at this early stage, I’m prepared to say it’s not a factor. 
Third, all missile fire occurs during this phase. So if you have a weapon with a rate of fire (RoF) greater than 1, now’s when you shoot your load. There are “auto-fire” rules which let you aim at a number of targets up to your weapon’s rate of fire. Roll to hit each target separately; damage dice from a successful hit equals RoF divided by number of targets (any remainder is added to the damage roll).
For example, a long bow’s rate of fire is 2; damage is 1d6. If I target 1 foe, I make 1 to-hit roll; damage is 2d6. If I target 2 foes, I make a to-hit roll for each; damage is 1d6 each.
Now is the time to cast spells, invoke magic items, read scrolls, quaff potions, rub your genie lamp, utter command words, and make any rolls required to maintain spells already in effect.  To keep things simple, I’m ruling that if you’re hit during a prior phase, you can’t cast a spell, but you probably can use a magic item.
This is a straight-up smack down on your foe, but you can’t be more than 1” away from your target. Roll 1d20 and add your class-based to-hit bonus; if the result equals or exceeds your target’s movement rate, the attack hits.
I’ll port over the various combat manoeuvres from Chimera, and there will be a tweak or two to the S&W guidelines for two-handed attacks and fighting with two weapons. Also need to playtest the S&W grappling rules a bit, though I’ll say now that they look good on paper.
I’ll probably need to come up with some rules for trying to get past a foe in melee range, as well as strategic withdrawal/retreat/flight, but more on that later. For the record, attacks of opportunity are right out.
This is a bookkeeping phase that every combatant can participate in. Mop-up is when you do your ammo checks, gear checks, wound inventory, weapon-readying, etc. It’s also when you apply the effects of persistent conditions, like long-term spells, environmental factors (like heat damage from fighting in a steam tunnel), and any other sort of round-to-round tallying.
Attack Rolls and Damage
Based on my ideas for damage, there are 4 3 outcomes to any attack roll:
Attack misses. Done. Maybe you take an initiative penalty if you miss with a natural “1”. Dunno.
Attack hits. Roll for damage, subtract armour, and apply the rest to target’s hit points.
Attack hits (natural d20 roll is in attacker’s critical range). Roll for damage, subtract armour, and apply the rest as a single wound (with wound severity equal to final damage result) 
Attack hits (modified d20 is exactly the number required to hit). Roll for damage using exploding die (i.e., when you roll the maximum amount, roll again and add the result; repeat until you no longer roll the highest value for that die), subtract armour, and apply the rest to the target’s hit points.
OK, there’s a lot here, but I’m open to feedback. Popular topics? My money is on movement die, using movement rate as an attack target number, and the exploding die thingie.
Rather than establish maximum range, I’d advocate reducing damage over distance. Perhaps half-damage if the total to-hit penalty exceeds the weapon’s range. For instance, a long bow’s range is 7”. If the to-hit penalty exceeds -7, you do 1d3 damage instead of 1d6.
I have guidelines that allow spell-casters to maintain certain spells by concentration, which requires a roll during the Magic phase..
A successful hit should always have a chance of inflicting damage, but some weapons don’t have the math (e.g., a 1d4 damage dagger vs. 6 points of plate mail). Hence the exploding damage die when you make a perfect strike. It only happens 5% of the time, but it’s still a chance. Let's make this simpler: when a critical hit is scored, the attacker has the option of inflicting damage as a wound or as 2 dice worth of hit points. So for weapons that can't penetrate armour (e.g., my 1d4 dagger vs. 6 points of plate), you get a chance to inflict more hit points, but not an actual wound. This also opens up the possibility of other results when a critical hit occurs, maybe depending on class. For example, a fighter might get his choice of: wound, double damage in hit points, disarm, push, or sweep. A magic-user who gets a critical might only get double damage in hit points option (because, hey, he's just a puny wizard, and like he's gonna drop anyone in a single blow anyway).