I was building a double rifled 12 bore,( single trigger ) that had a problem. It doubled on me 5 times with Brenneke Black Magic 3 in slugs (600 grs. each ) at 1500 fps. It will get your attn. in a 7 3/4 pound gun. I found that the bolt that runs from bottom tang to the top tang, when loosened would cause it to double. It happened twice while sitting at the bench and 3 times standing. Recoil was stout but manageable. Don't try it on purpose, if you have two fingers in the trigger guard you can break them both. Once when i was a kid i fired both bbls on a sawed off shotgun from the hip on a dare. It was 1962, didn't get out of the hospital till 11:30 that night, broke first and second finger, second finger had the bone pushed through when the gun flew out of my hand. Rich