diff --git a/include/ship.h b/include/ship.h
index c3e24a44..ea323c1f 100644
--- a/include/ship.h
+++ b/include/ship.h
@@ -185,5 +185,6 @@ extern int m_glim(struct mchrstr *, int);
 
 extern int shp_dchrg(struct shpstr *);
 extern int shp_fire(struct shpstr *);
+extern int shp_torp(struct shpstr *, int);
 
 #endif
diff --git a/src/lib/commands/mfir.c b/src/lib/commands/mfir.c
index be1ee2dc..19f1885c 100644
--- a/src/lib/commands/mfir.c
+++ b/src/lib/commands/mfir.c
@@ -708,7 +708,7 @@ quiet_bigdef(int attacker, struct emp_qelem *list, natid own, natid aown,
 	     coord ax, coord ay, int *nfiring)
 {
     int range;
-    double erange, hitchance;
+    double erange;
     struct shpstr ship;
     struct lndstr land;
     struct nstr_item ni;
@@ -738,45 +738,25 @@ quiet_bigdef(int attacker, struct emp_qelem *list, natid own, natid aown,
 	if (ship.shp_own == aown)
 	    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,
-				       I_SHELL, SHP_TORP_SHELLS - shell);
-	    if (shell < SHP_TORP_SHELLS)
-		continue;
-	    if (gun < 1)
-		continue;
-/*
-  if (ship.shp_mobil <= 0)
-  continue;
-*/
 	    erange = torprange(&ship);
 	    range = mapdist(ship.shp_x, ship.shp_y, ax, ay);
 	    if (range > roundrange(erange))
 		continue;
 	    if (!line_of_sight(NULL, ship.shp_x, ship.shp_y, ax, ay))
 		continue;
-
+	    dam2 = shp_torp(&ship, 0);
+	    /* no putship(&ship) because ammo is charged in use_ammo() */
+	    if (dam2 < 0)
+		continue;
 	    (*nfiring)++;
 	    fp = malloc(sizeof(struct flist));
 	    memset(fp, 0, sizeof(struct flist));
 	    fp->type = targ_ship;
 	    fp->uid = ship.shp_uid;
 	    add_to_fired_queue(&fp->queue, list);
-/*
-  nreport(ship.shp_own, N_FIRE_BACK, player->cnum, 1);
-*/
-	    hitchance = DTORP_HITCHANCE(range, ship.shp_visib);
-	    if (!chance(hitchance))
+	    if (!chance(DTORP_HITCHANCE(range, ship.shp_visib)))
 		continue;
-
-	    dam += TORP_DAMAGE();
+	    dam += dam2;
 	} else {
 	    erange = effrange(ship.shp_frnge, ship.shp_tech);
 	    if (roundrange(erange) < ni.curdist)
diff --git a/src/lib/commands/torp.c b/src/lib/commands/torp.c
index 207528ec..41490979 100644
--- a/src/lib/commands/torp.c
+++ b/src/lib/commands/torp.c
@@ -56,7 +56,6 @@ torp(void)
     natid vshipown;
     int range;
     int dam;
-    int shells;
     int subno;
     int victno;
     int erange;
@@ -79,11 +78,8 @@ torp(void)
 	    continue;
 	if ((mchr[(int)sub.shp_type].m_flags & M_TORP) == 0)
 	    continue;
-	shells = sub.shp_item[I_SHELL];
-	if (shells < SHP_TORP_SHELLS)
-	    shells += supply_commod(sub.shp_own, sub.shp_x, sub.shp_y,
-				    I_SHELL, SHP_TORP_SHELLS - shells);
-	if (sub.shp_item[I_GUN] == 0 || shells < SHP_TORP_SHELLS)
+	if (sub.shp_item[I_GUN] == 0
+	    || sub.shp_item[I_SHELL] < SHP_TORP_SHELLS)
 	    continue;
 	if (sub.shp_item[I_MILIT] < 1)
 	    continue;
@@ -106,11 +102,8 @@ torp(void)
 	       sub.shp_uid, mchr[(int)sub.shp_type].m_name);
 	    continue;
 	}
-	shells = sub.shp_item[I_SHELL];
-	if (shells < SHP_TORP_SHELLS)
-	    shells += supply_commod(sub.shp_own, sub.shp_x, sub.shp_y,
-				    I_SHELL, SHP_TORP_SHELLS - shells);
-	if (sub.shp_item[I_GUN] == 0 || shells < SHP_TORP_SHELLS) {
+	if (sub.shp_item[I_GUN] == 0
+	    || sub.shp_item[I_SHELL] < SHP_TORP_SHELLS) {
 	    pr("Ship #%d has insufficient armament\n", sub.shp_uid);
 	    continue;
 	}
@@ -149,19 +142,22 @@ torp(void)
 		continue;
 	    }
 	}
+	dam = shp_torp(&sub, 1);
+	sub.shp_mission = 0;
+	putship(sub.shp_uid, &sub);
+	if (CANT_HAPPEN(dam < 0)) {
+	    pr("Ship #%d has insufficient armament\n", sub.shp_uid);
+	    continue;
+	}
+
 	if ((mchr[(int)sub.shp_type].m_flags & M_SUB) == 0)
 	    anti_torp(sub.shp_uid, ntorping, vshipown);
 	getship(sub.shp_uid, &sub);
-	if (sub.shp_own == 0) {
+	if (sub.shp_own == 0)
 	    continue;
-	}
+
 	erange = roundrange(torprange(&sub));
 	pr("Effective torpedo range is %d.0\n", erange);
-	shells -= SHP_TORP_SHELLS;
-	sub.shp_item[I_SHELL] = shells;
-	putship(sub.shp_uid, &sub);
-	/* Mob cost for a torp is equal to the cost of 1/2 sector of movement */
-	sub.shp_mobil -= shp_mobcost(&sub) / 2.0;
 	pr("Whooosh... ");
 	getship(victno, &vship);
 	vshipown = vship.shp_own;
@@ -183,9 +179,8 @@ torp(void)
 	    }
 	} else if (range > erange) {
 	    pr("Out of range\n");
-	} else if (hitchance >= 1.0 || chance(hitchance)) {
+	} else if (chance(hitchance)) {
 	    pr("BOOM!...\n");
-	    dam = TORP_DAMAGE();
 	    if (vshipown != 0)
 		wu(0, vshipown, "%s in %s torpedoed %s for %d damage.\n",
 		   prsub(&sub), xyas(sub.shp_x, sub.shp_y, vshipown),
@@ -210,8 +205,7 @@ torp(void)
 		wu(0, vshipown, "Torpedo sighted @ %s by %s\n",
 		   xyas(sub.shp_x, sub.shp_y, vshipown), prship(&vship));
 	}
-	sub.shp_mission = 0;
-	putship(sub.shp_uid, &sub);
+
 	if (mchr[(int)sub.shp_type].m_flags & M_SUB)
 	    anti_torp(sub.shp_uid, ntorping, vshipown);
     }
@@ -355,55 +349,28 @@ static int
 fire_torp(struct shpstr *sp, struct shpstr *targ, int ntargets)
 {
     int range, erange, dam;
-    int shells;
-    double hitchance;
 
     erange = roundrange(torprange(sp));
     range = mapdist(sp->shp_x, sp->shp_y, targ->shp_x, targ->shp_y);
     if (range > erange)
 	return 0;
 
-    shells = sp->shp_item[I_SHELL];
-
-    if (shells < SHP_TORP_SHELLS)
-	shells += supply_commod(sp->shp_own, sp->shp_x, sp->shp_y,
-				I_SHELL, SHP_TORP_SHELLS - shells);
-
-    if (sp->shp_item[I_GUN] == 0 || shells < SHP_TORP_SHELLS)
-	return 0;
-
-    if (sp->shp_item[I_MILIT] < 1)
-	return 0;
-
-    if (sp->shp_effic < 60)
-	return 0;
-
-    if (sp->shp_mobil <= 0)
-	return 0;
-
     if (!line_of_sight(NULL, sp->shp_x, sp->shp_y,
 		       targ->shp_x, targ->shp_y))
 	return 0;
-
-    /* All set.. fire! */
-    shells -= SHP_TORP_SHELLS;
-    sp->shp_item[I_SHELL] = shells;
+    dam = shp_torp(sp, 1);
     putship(sp->shp_uid, sp);
-
-    /* Mob cost for a torp is equal to the cost of 1/2 sector of movement */
-    sp->shp_mobil -= shp_mobcost(sp) / 2.0;
-
-    hitchance = DTORP_HITCHANCE(range, sp->shp_visib);
+    if (dam < 0)
+	return 0;
 
     pr("Captain! Torpedoes sighted!\n");
 
-    if (chance(hitchance)) {
+    if (chance(DTORP_HITCHANCE(range, sp->shp_visib))) {
 	pr("BOOM!...\n");
 	if (sp->shp_own != 0)
 	    wu(0, sp->shp_own, "%s @ %s torpedoed %s\n",
 	       prship(sp),
 	       xyas(sp->shp_x, sp->shp_y, sp->shp_own), prsub(targ));
-	dam = TORP_DAMAGE();
 	if (ntargets > 2)
 	    dam /= ntargets / 2;
 
diff --git a/src/lib/subs/landgun.c b/src/lib/subs/landgun.c
index 7d463fd4..1cca07cd 100644
--- a/src/lib/subs/landgun.c
+++ b/src/lib/subs/landgun.c
@@ -33,6 +33,7 @@
 
 #include <config.h>
 
+#include "damage.h"
 #include "file.h"
 #include "nat.h"
 #include "optlist.h"
@@ -151,6 +152,33 @@ shp_dchrg(struct shpstr *sp)
     return (int)seagun(sp->shp_effic, 3);
 }
 
+/*
+ * Fire torpedo from ship SP.
+ * Use ammo and mobility, resupply if necessary.
+ * Return damage if the ship fires, else -1.
+ */
+int
+shp_torp(struct shpstr *sp, int usemob)
+{
+    int shells;
+
+    if (sp->shp_effic < 60 || (mchr[sp->shp_type].m_flags & M_TORP) == 0)
+	return -1;
+    if (sp->shp_item[I_MILIT] == 0 || sp->shp_item[I_GUN] == 0)
+	return -1;
+    if (usemob && sp->shp_mobil <= 0)
+	return -1;
+    shells = sp->shp_item[I_SHELL];
+    shells += supply_commod(sp->shp_own, sp->shp_x, sp->shp_y,
+                           I_SHELL, SHP_TORP_SHELLS - shells);
+    if (shells < SHP_TORP_SHELLS)
+       return -1;
+    sp->shp_item[I_SHELL] = shells - SHP_TORP_SHELLS;
+    if (usemob)
+	sp->shp_mobil -= (int)shp_mobcost(sp) / 2.0;
+    return TORP_DAMAGE();
+}
+
 /*
  * Return effective firing range for range factor RNG at tech TLEV.
  */
diff --git a/src/lib/subs/mission.c b/src/lib/subs/mission.c
index e45e1e2a..1f8e9d73 100644
--- a/src/lib/subs/mission.c
+++ b/src/lib/subs/mission.c
@@ -507,34 +507,15 @@ 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];
-		if (gun < 1)
-		    continue;
-		shell = sp->shp_item[I_SHELL];
-		if (shell < SHP_TORP_SHELLS)
-		    shell += supply_commod(sp->shp_own,
-					   sp->shp_x, sp->shp_y, I_SHELL,
-					   SHP_TORP_SHELLS - shell);
-		if (shell < SHP_TORP_SHELLS)
-		    continue;
-
 		range = roundrange(torprange(sp));
 		if (md > range)
 		    continue;
-
 		if (!line_of_sight(NULL, x, y, gp->x, gp->y))
 		    continue;
-		sp->shp_item[I_SHELL] = shell - SHP_TORP_SHELLS;
-		sp->shp_mobil -= shp_mobcost(sp) / 2.0;
+		dam2 = shp_torp(sp, 1);
 		putship(sp->shp_uid, sp);
+		if (dam2 < 0)
+		    continue;
 		hitchance = DTORP_HITCHANCE(md, sp->shp_visib);
 
 		wu(0, sp->shp_own,
@@ -546,7 +527,7 @@ perform_mission(coord x, coord y, natid victim, struct emp_qelem *list,
 		   "\tWhooosh... Hitchance = %d%%\n",
 		   (int)(hitchance * 100));
 
-		if (hitchance < 1.0 && !chance(hitchance)) {
+		if (!chance(hitchance)) {
 		    wu(0, sp->shp_own, "\tMissed\n");
 		    mpr(victim,
 			"Incoming torpedo sighted @ %s missed (whew)!\n",
@@ -554,8 +535,6 @@ perform_mission(coord x, coord y, natid victim, struct emp_qelem *list,
 		    continue;
 		}
 		wu(0, sp->shp_own, "\tBOOM!...\n");
-		dam2 = TORP_DAMAGE();
-
 		dam += dam2;
 		nreport(victim, N_TORP_SHIP, 0, 1);
 		wu(0, sp->shp_own,