Thank you and I would assume that you’d be legally safe as I’ve bought rear sights and other items sent for the U.K. in the past. However, I have a couple No4 micrometer sights already, I just don’t want to grind them down if I don’t have to in case I need them for future rifles. That’s why a pre-milled No5 Sight makes more sense in light of it never being used for shooting... And even if it is in the future, like with all my No4 rifles, I’ll zero at 200 and then learn my actual click adjustments for farther out and not rely on the marks designed for a Mk VII round I’m not using.