The missing threads are supposedly to identify each different caliber of barrel on the short actions, but Dangerous Dan, who has taken off many barrels on the XS rifles says that they're all the same. What he believes it is is remington cutting ahead of the relief cut on their barrel shanks for the model 700 barrels to save money putting them on the XS7's. It does not compromise safety. If you see a Marlin XS7 with an REP proof stamp on the RIGHT side of the barrel, chances are it will be missing threads in the exact same spot. As far as trigger guards breaking, I have 4 savages including my XL7 with a plastic trigger guard and I've never broken one, and put one of the savages through some hard hunting. With the extractor, I've never heard of anything wrong with it, but I have heard of them flying out of the bolt. Just be careful with it.