Thanks for posting this thread. I thought I was the only one with this problem. I have a 9mm Baretta 92 SB Compact that jams with every single hollow point I put in it. We polished the feed ramp by hand to no avail, and never thought to use the Dremmel and some polishing compound. We'll surely give it a try and write back.
I second the motion for the Dremel tool with a polishing wheel on it. It will polish your feed ramp to an extremely bright, mirror-like shine without eating away too much material. You'll want to do a whole bunch of misc. parts on your gun after doing it!
I used Mother's Mag & Aluminum polish as the compound. It will polish steel just as good as it does aluminum!
If you must polish - use a small dremel and MAAS polishing cream (or mothers). You want to be very careful not to take too much from the ramp, make it uneven, or inadvertently round the lower lip. IF - the HPs are hanging on the lip, could be the pistol just won't run those types - try something with a little more rounded with less opening, go to the Corbon powerball, or use a FMJ. Could also be a slight mis-match between the frame (locking insert I think has a portion of ramp) and bottom of the ramp/barrel. I don't know much about the Sigs, but the locking insert ramp is probably coated with something and should not be polished off??
I polish the feed ramps of all the guns i work on with a dremel and a wire brush... though i have never heard of a sig 225 having feeding problems ensure you magazine is seating all the way and check for major burrs in the edge of the feed ramp. If the polishing doesnt work, try softening the edge of the feed ramp, but do not remove any more than a hundreth of an inch. if you go to far with this you will have to replace the barrel