Agreeably, the mentions of practice are solid advice, but we all owe our quarry practice every year before we head to the marsh, field, or woods. It ensures that our equipment is still functioning correctly, and knocks any rust off our abilities that may have developed during those periods of too much work, not enough play. If you are getting good hits, and still only crippling birds, range could be an issue when using steel. You can obviously try to wait for birds to get closer, but depending on where you're hunting, how educated the birds have become, etc. sometimes make that easier said than done. I personally have literally shot the feathers off a wood duck hen and stopped her in flight and then watched as she flew off crippled because of steel. I now shoot nothing but HeviShot or HeviMetal. HeviMetal is comparable in price to Blackcloud, Blindside, and other premium steel shot but it has half a load of HeviShot in it so I get better pattern density and the lethality of denser shot at longer ranges. Of course, you'll need to pattern to test your gun/choke combo, but I'd recommend giving it a try.