diff --git a/include/ship.h b/include/ship.h
index 99f945de..c3e24a44 100644
--- a/include/ship.h
+++ b/include/ship.h
@@ -184,5 +184,6 @@ extern int m_frnge(struct mchrstr *, int);
 extern int m_glim(struct mchrstr *, int);
 
 extern int shp_dchrg(struct shpstr *);
+extern int shp_fire(struct shpstr *);
 
 #endif
diff --git a/src/lib/commands/mfir.c b/src/lib/commands/mfir.c
index 632847f3..08185a3f 100644
--- a/src/lib/commands/mfir.c
+++ b/src/lib/commands/mfir.c
@@ -82,7 +82,6 @@ multifire(void)
     int gun;
     int shell;
     int shots;
-    double guneff;
     int dam;
     int totaldefdam = 0;
     int fshipno;
@@ -189,13 +188,11 @@ multifire(void)
 		pr("Not enough mil on ship #%d\n", item.ship.shp_uid);
 		continue;
 	    }
-	    gun = item.ship.shp_item[I_GUN];
-	    gun = MIN(gun, item.ship.shp_glim);
-	    if (item.ship.shp_frnge == 0) {
+	    if (item.ship.shp_glim == 0) {
 		pr("Ships %d cannot fire guns!\n", item.ship.shp_uid);
 		continue;
 	    }
-	    if (gun == 0) {
+	    if (item.ship.shp_item[I_GUN] == 0) {
 		pr("Not enough guns on ship #%d\n", item.ship.shp_uid);
 		continue;
 	    }
@@ -328,29 +325,16 @@ multifire(void)
 		if (target == targ_sub)
 		    /* Don't tell it's a sub */
 		    range2 = -1;
-		gun = fship.shp_item[I_GUN];
-		gun = MIN(gun, fship.shp_glim);
-		if (fship.shp_frnge == 0 || gun == 0) {
+		if (fship.shp_item[I_GUN] == 0) {
 		    pr("Insufficient arms.\n");
 		    continue;
 		}
-		shell = fship.shp_item[I_SHELL];
-		shell += supply_commod(fship.shp_own,
-				       fship.shp_x, fship.shp_y,
-				       I_SHELL, 2 - shell);
-		if (shell <= 0) {
+		dam = shp_fire(&fship);
+		putship(fship.shp_uid, &fship);
+		if (dam <= 0) {
 		    pr("Klick!     ...\n");
 		    continue;
 		}
-		gun = MIN(gun, shell * 2);
-		gun = MIN(gun, mil / 2);
-		gun = MAX(gun, 1);
-		shots = gun;
-		guneff = seagun(fship.shp_effic, shots);
-		dam = (int)guneff;
-		shell -= ldround(shots / 2.0, 1);
-		fship.shp_item[I_SHELL] = shell;
-		putship(fship.shp_uid, &fship);
 	    }
 	    if (opt_NOMOBCOST == 0) {
 		fship.shp_mobil = MAX(fship.shp_mobil - 15, -100);
@@ -723,7 +707,7 @@ static int
 quiet_bigdef(int attacker, struct emp_qelem *list, natid own, natid aown,
 	     coord ax, coord ay, int *nfiring)
 {
-    int nshot, range;
+    int range;
     double erange, hitchance;
     struct shpstr ship;
     struct lndstr land;
@@ -753,16 +737,13 @@ quiet_bigdef(int attacker, struct emp_qelem *list, natid own, natid aown,
 	/* Don't shoot yourself */
 	if (ship.shp_own == aown)
 	    continue;
-	if (ship.shp_effic < 60)
-	    continue;
-
-	gun = ship.shp_item[I_GUN];
-	shell = ship.shp_item[I_SHELL];
-
-	if (ship.shp_item[I_MILIT] < 1)
-	    continue;
-
 	if (mchr[(int)ship.shp_type].m_flags & M_SUB) {
+	    if (ship.shp_effic < 60)
+		continue;
+	    gun = ship.shp_item[I_GUN];
+	    shell = ship.shp_item[I_SHELL];
+	    if (ship.shp_item[I_MILIT] < 1)
+		continue;
 	    if (shell < SHP_TORP_SHELLS)
 		shell += supply_commod(ship.shp_own,
 				       ship.shp_x, ship.shp_y,
@@ -800,16 +781,9 @@ quiet_bigdef(int attacker, struct emp_qelem *list, natid own, natid aown,
 	    erange = effrange(ship.shp_frnge, ship.shp_tech);
 	    if (roundrange(erange) < ni.curdist)
 		continue;
-	    /* must have gun, shell, and milit to fire */
-	    if (shell < 1)
-		shell += supply_commod(ship.shp_own,
-				       ship.shp_x, ship.shp_y, I_SHELL, 1);
-	    /* only need 1 shell, so don't check that */
-	    if (shell < 1)
-		continue;
-	    nshot = MIN(gun, ship.shp_item[I_MILIT]);
-	    nshot = MIN(nshot, ship.shp_glim);
-	    if (nshot == 0)
+	    dam2 = shp_fire(&ship);
+	    /* no putship(&ship) because ammo is charged in use_ammo() */
+	    if (dam2 < 0)
 		continue;
 	    (*nfiring)++;
 	    fp = malloc(sizeof(struct flist));
@@ -818,7 +792,7 @@ quiet_bigdef(int attacker, struct emp_qelem *list, natid own, natid aown,
 	    fp->uid = ship.shp_uid;
 	    add_to_fired_queue(&fp->queue, list);
 	    nreport(ship.shp_own, N_FIRE_BACK, player->cnum, 1);
-	    dam += seagun(ship.shp_effic, nshot);
+	    dam += dam2;
 	}
     }
     snxtitem_dist(&ni, EF_LAND, ax, ay, 8);
diff --git a/src/lib/commands/miss.c b/src/lib/commands/miss.c
index d859d564..28161874 100644
--- a/src/lib/commands/miss.c
+++ b/src/lib/commands/miss.c
@@ -221,7 +221,7 @@ mission(void)
 	    radius = desired_radius;
 
 	if ((mission == MI_INTERDICT) && (type == EF_SHIP))
-	    if (mchr[(int)gp->type].m_frnge < 1) {
+	    if (mchr[(int)gp->type].m_glim == 0) {
 		pr("%s: cannot fire at range!\n", obj_nameof(gp));
 		continue;
 	    }
diff --git a/src/lib/commands/torp.c b/src/lib/commands/torp.c
index 9a10dbf5..8df3305b 100644
--- a/src/lib/commands/torp.c
+++ b/src/lib/commands/torp.c
@@ -319,30 +319,12 @@ static void
 fire_dchrg(struct shpstr *sp, struct shpstr *targ, int ntargets)
 {
     int dam;
-    int shells;
-    int gun;
-    double guneff;
 
     if ((mchr[(int)targ->shp_type].m_flags & M_SUB) == 0) {
-	shells = sp->shp_item[I_SHELL];
-	gun = sp->shp_item[I_GUN];
-	gun = MIN(gun, sp->shp_glim);
-	gun = MIN(gun, sp->shp_item[I_MILIT] / 2);
-
-	shells += supply_commod(sp->shp_own, sp->shp_x, sp->shp_y,
-				I_SHELL, (gun + 1) / 2 - shells);
-
-	gun = MIN(gun, shells * 2);
-	if (gun == 0)
-	    return;
-
-	/* ok, all set.. now, we shoot */
-	shells -= ldround(gun / 2.0, 1);
-	sp->shp_item[I_SHELL] = shells;
+	dam = shp_fire(sp);
 	putship(sp->shp_uid, sp);
-
-	guneff = seagun(sp->shp_effic, gun);
-	dam = (int)guneff;
+	if (dam < 0)
+	    return;
 	if (ntargets > 2)
 	    dam /= ntargets / 2;
 
diff --git a/src/lib/subs/fortdef.c b/src/lib/subs/fortdef.c
index e11d7afc..591fc0f2 100644
--- a/src/lib/subs/fortdef.c
+++ b/src/lib/subs/fortdef.c
@@ -67,12 +67,10 @@ int
 sd(natid att, natid own, coord x, coord y, int noisy, int defending,
    int usesubs)
 {
-    int nshot;
     int range;
     double eff;
     struct shpstr ship;
     struct nstr_item ni;
-    int shell;
     int dam, rel, rel2;
 
     if (own == 0)
@@ -91,34 +89,23 @@ sd(natid att, natid own, coord x, coord y, int noisy, int defending,
 	rel2 = getrel(getnatp(ship.shp_own), att);
 	if ((ship.shp_own != own) && ((rel != ALLIED) || (rel2 != AT_WAR)))
 	    continue;
-	if (ship.shp_effic < 60)
-	    continue;
 	if ((mchr[(int)ship.shp_type].m_flags & M_SUB) && !usesubs)
 	    continue;
 	range = roundrange(effrange(ship.shp_frnge, ship.shp_tech));
 	if (range < ni.curdist)
 	    continue;
-	/* must have gun, shell, and milit to fire */
-	shell = ship.shp_item[I_SHELL];
-	if (shell < ship.shp_glim)
-	    shell += supply_commod(ship.shp_own, ship.shp_x, ship.shp_y,
-				   I_SHELL, shell - ship.shp_glim);
-	nshot = MIN(MIN(ship.shp_item[I_GUN], shell), ship.shp_item[I_MILIT]);
-	nshot = MIN(nshot, ship.shp_glim);
-	if (nshot <= 0)
-	    continue;
-	ship.shp_item[I_SHELL] = shell - nshot;
+	dam = shp_fire(&ship);
 	putship(ship.shp_uid, &ship);
+	if (dam < 0)
+	    continue;
 	if (defending)
 	    nreport(ship.shp_own, N_FIRE_BACK, att, 1);
 	else
 	    nreport(ship.shp_own, N_FIRE_S_ATTACK, att, 1);
-	dam = seagun(ship.shp_effic, nshot);
 	eff *= (1.0 - (0.01 * dam));
 	if (noisy) {
 	    pr_beep();
-	    pr("Incoming shell%s %d damage!\n",
-	       nshot == 1 ? " does" : "s do", dam);
+	    pr("Incoming shells do %d damage!\n", dam);
 	}
 	if (noisy || (ship.shp_own != own)) {
 	    if (ship.shp_own == own)
diff --git a/src/lib/subs/landgun.c b/src/lib/subs/landgun.c
index bd66b7f6..7d463fd4 100644
--- a/src/lib/subs/landgun.c
+++ b/src/lib/subs/landgun.c
@@ -101,6 +101,33 @@ fort_fire(struct sctstr *sp)
     return (int)fortgun(sp->sct_effic, guns);
 }
 
+/*
+ * Fire from ship SP.
+ * Use ammo, resupply if necessary.
+ * Return damage if the ship fires, else -1.
+ */
+int
+shp_fire(struct shpstr *sp)
+{
+    int guns, shells;
+
+    if (sp->shp_effic < 60)
+	return -1;
+    guns = sp->shp_glim;
+    guns = MIN(guns, sp->shp_item[I_GUN]);
+    guns = MIN(guns, (sp->shp_item[I_MILIT] + 1) / 2);
+    if (guns == 0)
+	return -1;
+    shells = sp->shp_item[I_SHELL];
+    shells += supply_commod(sp->shp_own, sp->shp_x, sp->shp_y,
+                           I_SHELL, (guns + 1) / 2 - shells);
+    guns = MIN(guns, shells * 2);
+    if (guns == 0)
+       return -1;
+    sp->shp_item[I_SHELL] = shells - (guns + 1) / 2;
+    return (int)seagun(sp->shp_effic, guns);
+}
+
 /*
  * Drop depth-charges from ship SP.
  * Use ammo, resupply if necessary.
diff --git a/src/lib/subs/mission.c b/src/lib/subs/mission.c
index 1d82a552..e45e1e2a 100644
--- a/src/lib/subs/mission.c
+++ b/src/lib/subs/mission.c
@@ -480,16 +480,10 @@ perform_mission(coord x, coord y, natid victim, struct emp_qelem *list,
 	    sp = (struct shpstr *)glp->thing;
 	    mcp = glp->cp;
 
-	    if (sp->shp_effic < 60)
-		continue;
-	    if (sp->shp_frnge == 0)
-		continue;
 	    if (((mission == MI_INTERDICT) ||
 		 (mission == MI_SINTERDICT)) &&
 		(md > ship_max_interdiction_range))
 		continue;
-	    if (sp->shp_item[I_MILIT] < 1)
-		continue;
 /*
   if ((mcp->m_flags & M_SUB) &&
   (sect.sct_type != SCT_WATER))
@@ -513,6 +507,12 @@ perform_mission(coord x, coord y, natid victim, struct emp_qelem *list,
    a sub. */
 		if (*s != 's')
 		    continue;
+		if (sp->shp_effic < 60)
+		    continue;
+		if (sp->shp_frnge == 0)
+		    continue;
+		if (sp->shp_item[I_MILIT] < 1)
+		    continue;
 		if (sp->shp_mobil < 0)
 		    continue;
 		gun = sp->shp_item[I_GUN];
@@ -569,28 +569,13 @@ perform_mission(coord x, coord y, natid victim, struct emp_qelem *list,
 		range = roundrange(effrange(sp->shp_frnge, sp->shp_tech));
 		if (md > range)
 		    continue;
-		if (mission == MI_SINTERDICT) {
+		if (mission == MI_SINTERDICT)
 		    dam2 = shp_dchrg(sp);
-		    putship(sp->shp_uid, sp);
-		    if (dam2 < 0)
-			continue;
-		} else {
-		    gun = sp->shp_item[I_GUN];
-		    gun = MIN(gun, sp->shp_glim);
-		    shell = sp->shp_item[I_SHELL];
-		    if (shell < gun)
-			shell += supply_commod(sp->shp_own,
-					       sp->shp_x, sp->shp_y, I_SHELL,
-					       gun - shell);
-		    gun = MIN(gun, shell);
-		    gun = MIN(gun, sp->shp_item[I_MILIT] / 2.0);
-		    if (gun == 0)
-			continue;
-		    gun = MAX(gun, 1);
-		    dam2 = seagun(sp->shp_effic, gun);
-		    sp->shp_item[I_SHELL] = shell - gun;
-		    putship(sp->shp_uid, sp);
-		}
+		else
+		    dam2 = shp_fire(sp);
+		putship(sp->shp_uid, sp);
+		if (dam2 < 0)
+		    continue;
 		if (range == 0.0)
 		    prb = 1.0;
 		else