For the return spring I found this one https://www.amazon.com/dp/B076LVYPYC?psc=1&ref=ppx_yo2ov_dt_b_product_details that was the hardest thing to find for the harrier, needed to have id big enough for a 19mm barrel, od smaller than 22mm to fit in the sled and clear the screws that hold the aluminum rails but have a wire diamter bigger than 1.2mm to be an upgrade from stock spring while not being to long as it needs to compress to really small length to allow for full prime