Quote Originally Posted by seanhagerty View Post
It looks like the bottom metal is for a long action, but it uses short action mags. Is this correct?
Yes. CDI makes two Savage 110 long action DBMs, one that uses AICS 300WM magazines and another than uses AICS 308 magazines. Mine pictured above is the LA/308 model.

If yes,at the top of the mag, is there a gap at the rear?
Yes, a small gap at the top near the mag, with a larger one if you don't use the extended bolt baffle.

The AICS 223 mag accepts 2.55", AICS/Accurate 308 mags accept roughly 2.87", Alpha Type IIs or modified AICS mags (front plate removed) take 2.95ish.