friend of mine has one of these, never had the courage to shoot it at his ranch. i have had a few friends take their best shot and wound up regretting it, they likened the feeling to the way you feel after a car wreck.
i will stick to .40 and .45 cals
just standing 20-30 feet away when this thing is fired can be felt. makes your hearing protection seem like it is not on and your body feels the impact. its amazing, but i will pass. afterall they just shoot birds and into the river on his property. the birds look great, because you definitely know if you hit them if you get my drift.