www.searcyent.com will do chopper lump bbls for a large extra cost. Go to the web site and then to the options page, you can find the cost there. Typically I think none of those listed in your question use chopper lump. I have heard that CL BBls sit closer to one another at the breech end, so this makes for easier/better regulation. I do not think that there is a strength issue, but I am just a reader of info others have written, I am NO DR smith.