...it is not as straight forward as the Sig X-five

There is a nasty hardened steel pin set in the cast alloy that is part of the breech lock up - it requires grinding down and then drilling out which requires a very steady hand and a strong nerve.

Once that's out it's the same story as the Sig - just a question of making a barrel with the same attributes as the original but that will take lead bb.

I am trying something a little different and didn't get it finished last night but when I do I shall post it up on here.