The other day a customer brought in a Rem 870 and said he just launched a turkey choke downrange could I please check the threads. I took the gun and visually checked the threads and they looked fine. tried a choke out of a new 870 and couldn't hardly get it to start. I wire brushed the threads and cleaned it out real goood. same thing? grabbed an old choke out of the drawer because I didn't want to mess up a new choke if it was going to be difficult, it worked great. Finger pressure was all that was needed to screw choke in and out. closer inspection revealed this one to be an invector thread. That was really weird. The owner swears it was purchased new in the box from a major Springfield, Missouri sporting goods retailer. There are no signs of the barrel having been shortened. Its ribbed and looks factory. Now that the problem is solved no big deal just curious if anyone else has come across this type of thing on a n.i.b. gun?