I have an M13 that I've been using with success in the front of my amp. I only use it for delay and modulation now, most tremolo, vibrato, chorus, and reverbs.
I'm wanting to run it though the effects loop on my amp.

The question is: Do I run the effects loop out into the input of the m13 then the out of the m13 into the effects return? Or is it more complicated than that?

Thanks in advance.
Guitar > M13 input > M13 output > amp input > amp fx send > m13 fx return > m13 fx send > amp fx return

This would allow you to use effects pre and post the amp's preamp (gain). I like my modulations before dirt but time based effects post. Also you'd still be able to use the drives in the modeler. If you're gonna run everything in the fx loop plug your guitar to the amp and start from the amp's fx send like written above.
Originally Posted by evening_crow
Quoting yourself is cool.

WARNING: I kill threads.