The ability to change an existing Vector receiver’s caliber is not and has never been a feature of the Vector platform.
There is no factory service option nor "conversion kit" available to convert a Vector receiver from one caliber to another.
This misconception for caliber interchangeability seems to come from a misunderstanding of the Vector platform’s parts compatibility. All GEN 2 Vector centerfire models share the same upper assembly which can be used on any centerfire Gen 2 Vector receiver, regardless of barrel length or caliber.
Example: You own a Gen 2 Vector CRB chambered in .45 ACP and you decide to purchase a Vector CRB, complete receiver only, chambered in 9mm. Your existing upper will work with your new 9mm Vector CRB receiver. You would need to replace the upper's .45 ACP ejection port with a 9mm ejection port, then you can install your existing upper onto the 9mm Vector CRB receiver.
There are two ejection ports in use with the centerfire Vector. The .45 ACP ejection port is also used with 10mm. The 9mm ejection port is also used with .40 S&W. The ejection port is easily replaced and may be purchased from our online store.
It is your responsibility to maintain a compliant firearm. For example, if you have a Vector CRB, which is classified as a rifle and has a stock installed, and you install that upper assembly without modification onto a Vector SDP receiver, which is classified as a pistol, you would be converting that pistol into a Short Barrel Rifle, which is an NFA item and requires a tax stamp.