Hi there -- I also have an XD40sc, and have been very happy with it. It has been very reliable and accurate. If anything, it is overbuilt.
1. I looked up grain and it is a unit of weight equal to 1/7000 of a pound -- so an 180 grain bullet is just over 4 tenths of an ounce.
2. 40 caliber pistols are LOUD, especially in a short barrel. People generally talk about the 40 as having a sharp recoil, and that relates to the bullet weight and velocity. 357's push smaller bullets at higher velocities, and are LOUDER. Use your hearing protection.
3. My XD40sc is surprisingly accurate for a 3" barrel. I think that the accuracy of the pistol is good out past 25-30 yards, but the short sight radius make ME less effective at those ranges. At self-defense distances of 7-15 yards, I think the XD40sc is very effective.
Good Luck with your XD40sc. I hope your experience is as positive as mine has been.