I've been using your U2 in my A5 and having great luck with it shooting Hevi-Shot's new lead loads at doves the past few days (Please note: Nothing larger than a #6 shot size can be used with our competition chokes). Yes, this is LEAD load being offered by Environ-Metal, and it's called Hevi-Lead. From what I've seen, it's good stuff and your U2 tube patterns it well. It must have more antimony that regular lead, because it hits doves hard.
-Jarrod Spilger, Freelance Outdoors Writer