How do you figure ibo speed in archery?

IBO speed is only determined with a 350 gr arrow, 30" long, at 70 lb draw weight, with nothing on the bow string except an arrow release loop. Even with these criteria exact, you still have to shoot through a chronograph to find your bow's exact speed. IBO speed is only determined with a 350 gr arrow, 30" long, at 70 lb draw weight, with nothing on the bow string except an arrow release loop. Even with these criteria exact, you still have to shoot through a chronograph to find your bow's exact speed.