Originally Posted by Brian.Samson
The expensive part in your idea is going to be the tube - that's the downside with 3D printing, it gets expensive when you start printing larger things. The tube alone would work out at something like £45 to print, possibly more because the diameter of the tube would need to be large enough to fit over the turrets so you could fit it. The ring I've designed can be smaller than the turrets because you can maneuver it to get it over them one at a time (if you see what I mean) and there's also a chance that because there's a small gap in my ring you could open the gap up enough to get it over the tube without needing to take the scope out of it's mounts (something I need to check with the prototype).
If you can find a tube that would fit over (a bit of plastic drainpipe etc) and let me know the ID and OD of it, I can design up a boss to fit it onto the scope for you and something to go on the other end with the yards marked on it.
Brian we aren't on the same page. I will try to do a video mockup to explain. Due to the design is that why you slide in on from the eye piece side rather than the objective side? My goal wouldn't be to have the tube printed. I'd use off the shelf CF or thin aluminum in some readily available size.