I have a clapped out boat anchor .45-70 trapdoor with faint traces of rifling, my Dad and I have been shooting .410 shotshells in it since the 1920's. Our experience, which does not apply to your question obviously, is that high velocity destroys any semblance of a pattern. Handloads of low power/velocity produce usable patterns and sufficient killing power for a garden gun as the English call them. Also have a Lee Metford single shot bolt action that shoots 2 1/2 inch .410...same thing, high velocity is useless, low velocity gives good patterns and kills ground squirrels and jackrabbits at 30 yards.
I am curious what you want to do with such a tiny shot load at 1100 to 1300 fps.
