Buck;
Not familular with the "J" lock.( Could send more Pic's)The brake is removable. I must say that such a good job was done on it that it is totally seamless and to look at it you would think it is not. The work was done here in Montana at this guy's shop. http://www.muzzlebrake.com/svc_acp.htmlI had his complete accuracy package as well. I don't have a thread protector for it as I never use the thing without the brake. I would like to keep it simple and sell as a package.
Thanks
Bob