I don't have a Radiant, or any Rugged centerfire can for that matter. I do however have an Oculus and it is built very similarly with the short and long configurations. I haven't had any problems with it coming loose and I've been very pleased with it's performance and build quality as well as engineering.
I would think with the Radiant that when you tighten it down onto the taper mount, that it would be pretty easy to check for tightness of the body at that time. I would also think there would be almost no way that it could come loose enough to come apart without you intending it to.