I have noticed there has been a recent glut of 40 caliber magazines with red baseplates for sale on GB. I would assume they were probably used to differentiate between types of ammunition in a training environment. As an example, I have two M & P 40 magazines with orange base plates. They came from a DOC training facility. They were only used during range training.
That makes sense. Thanks for the reply. I have a 411 with only one mag and I am finding it hard to locate a few more. Will any of the other .40 mags out there fit this? I haven't had much experience with S&W pistols before.