XdM compact

[Gryff]

This is a newbi question. Although I've own a older 9mm handgun, what is the magazine disconnect?

A pistol with a magazine disconnect cannot fire if there is no magazine in the gun.

I would of thought the regular xd magazine would fit on the M version!

No, they definitely will not.

I wonder why they didn't just make a regular 4" barrel instead of a 3.8". Kind of odd don't you guys think?

Since the regular XDm has a 4.5" barrel, I figure they wanted to shorten it by more than .5 inches to help differentiate it.