marshi gun tweaks (#4880)

Small PR. Makes the mamba a normal sized item when folded. Why was this gun the same size as the avg bagable rifle? Defeats the point of a folding stock.

Makes the copperhead no longer fit in a backpack at CDBs request.

code/modules/projectiles/guns/projectile/automatic/mamba.dm

@@ -8,7 +8,7 @@
 	item_state = "mamba"
 	icon = 'icons/obj/guns/projectile/mamba.dmi'
 	fire_sound = 'sound/weapons/guns/fire/carbine.ogg'
-	w_class = ITEM_SIZE_BULKY
+	w_class = ITEM_SIZE_NORMAL
 	slot_flags = SLOT_BACK
 	caliber = CAL_LRIFLE
 	load_method = SINGLE_CASING|MAGAZINE
@@ -70,7 +70,7 @@
 	item_state = "copperhead"
 	icon = 'icons/obj/guns/projectile/copperhead.dmi'
 	fire_sound = 'sound/weapons/guns/fire/rifle.ogg'
-	w_class = ITEM_SIZE_BULKY
+	w_class = ITEM_SIZE_HUGE
 	slot_flags = SLOT_BACK
 	caliber = CAL_RIFLE
 	load_method = SINGLE_CASING|MAGAZINE