@sw40ve515: Nice to see another person from DM. My best OWB holster for the Sigma is my Fobus HK-1. It works great. I don't know about Galco, I have an IWB leather holster from Georgia Holster Group in size Medium that fits my Sigma like a glove. It conceals well.
Here are my Sigma .40 tips:
180 grain seems to work best for me
Some people seem to shoot it very well; I do suspect the gun is mechanically accurate. However, many do not shoot it with exceptional accuracy, myself included. I have managed to get and stay on the target, but only by working hard at it. I do suspect the Sigma got me to work out my technique and make me a better shooter. I just got a Springfield XDm .45 and from my very first shot am shooting bullseyes. I can even stitch overlapping holes at 25 yards. But, when I switch back to my Sigma 5 seconds later, I'm grouping everything low by about 8-10 inches. I switch back to the XDm and start ripping the center ring out of the target.
Why?
My best guess is either the trigger break (which is something I need to work on my technique and/or do some work on the trigger to smooth it), or it's the sights (perhaps my sights are off?), or the .40 goes low? (I doubt it).
But, at least I know that my grip, sighting, stance, breathing, etc are all ok.
If you are dead on, then great! If you're not... then work on your technique first and possibly your trigger next.