I don't have 1st hand experience with the XDM 45 yet but the XDM9 and 40 both function without issue. It's my understanding that the slide rib design is altered in the XDM platform versus the original HS-2000/XD and this adjustment allows SWC designs to feed reliably. My searches around xdtalk.com only ever find in threads with fairly "parrotlike" posts without any solid verifiable information to back up their claims both in favor and against shooting SWC styles.
As a sidenote, Missouri Bullet Company's 12 BHN Bullseye #2 LSWC (H&G #68 mimic I think?) seated at a very long OAL of 1.275" has functioned 100% reliably in the 100 rounds sample pack I ordered. That far out, they barely fit in the magazine but the "shoulder nicking" is the most forgiving of any length I've tested. 4.6gr/HP-38 never gored or deformed any shoulders enough to create any noteworthy accuracy issues. ~2" groups at 10 yards of 10 shots versus my usual ~1" ragged hole is satisfactory for my IDPA purposes.
Hoping for some solid info to be posted that really holds some water =)
~ Jech