rdd - keep in mind that those barrels could have been laying around in someone's shop for a long time before being used in this gun. Anybody's guess when, where, or from whom Bonehill got them. The USA guns were on the cheap/machine made side for Brit guns. So, these could easily have been some bargain basement barrels. I'd not be surprised if they were of Belgian origin, either. To get any kind of fix on them, we need to seem more similar with something identifiable as to source and/or age.