using the Read More function in a custom fileld

I’m probably doing something pretty crazy, and of course I’m having some trouble with it.

I have a site with a listing of posts that all have the same format. So I use custom fields pretty extensively. I then have a single private post that has a post template. I use a custom posts shortcode in all of my posts to call the post template field in my templates post. the template has custom fields shortcodes in it as well. Essentially I’m doing some nested shortcodes/custom fields. This is all working pretty well actually.
My problem is this. I have the < !–More– > in my template customfield, but when it gets called on my live site it is not getting generated properly. when viewing the source of my front page the shortcode is actually just showing up as a standard HTML comment. It looks like WP is not picking it up as a function to be run.

I guess what I am looking for is a ‘More’ shortcode but I haven’t found anything.