What makes Spears do double damage on Jump?

What the game is doing at C2/1512 is checking the actual item number of your equipped weapon to see if it's in the range that the spears fall in; items 29-36.
If you want to have more weapons count as spears for jumping, it would be easiest if all of them were still lumped in one continuous section of the item list so that you could simply change the values in the function to match the new range.

Code:

C2/1512: C9 1D CMP #$1D   <-item number of first spear
C2/1514: 90 08 BCC $151E (Exit if item number less than first spear)
C2/1516: C9 25 CMP #$25   <-item number of last spear +1
C2/1518: B0 04 BCS $151E (Exit if item number greater than last spear)
C2/151A: A9 02 LDA #$02
C2/151C: 85 BD STA $BD
C2/151E: 60 RTS