FWIW I've never considered #12 shot, which is what I've always been told is in 22RF shotshells, to be bird shot. They were, however, fully up to the task of breaking the cracker sized clay "hummingbirds" that we shot at Boy Scout camp firing range. The game, trap and targets were dubbed MoSkeetO brand. I just wish I could remember the ranges at which we shot them. Though I cannot, I do believe we broke some of them at more than 5 yards. Granted, killing a bird outright, without wounding it to die a slow death later, is not the same as chipping a clay target.
Why don't you pattern some, and do a penetration test at the same time?
I would love to have one of the Remington smoothbores designed for these shells but have never gotten up the gumption to pay the prices a nice one brings today. Wingshooting carpenter bees around the barn and sheds would be super fun with one.
