Firing pin acquisition 2: electric boogaloo (#5684)

* Adds a box of firing pins to the RD's locker. Can't permit mass-production of firing pins via R&D, sorry lads, this is the best anyone can do.
* This box of pins has a varied assortment of pin types.
* Pin removal is based on probability as the screwdriver is the only means of removing pins at the moment.

code/modules/projectiles/gun.dm

@@ -725,7 +725,7 @@ obj/item/weapon/gun/Destroy()
 	if(isscrewdriver(I))
 		visible_message("<span class = 'warning'>[user] begins to try and pry out [src]'s firing pin!</span>")
 		if(do_after(user,45 SECONDS,act_target = src))
-			if(pin.durable)
+			if(pin.durable || prob(50))
 				visible_message("<span class = 'notice'>[user] pops the [pin] out of [src]!</span>")
 				pin.forceMove(get_turf(src))
 				pin = null//clear it out.
@@ -736,4 +736,4 @@ obj/item/weapon/gun/Destroy()
 				"You hear a metallic crack.")
 				qdel(pin)
 				pin = null
-	.=..()
+	.=..()