Ok, so I've had my XCR for a couple of months but just recently been able to go to the range - I put about 300 rounds (Winchester and PMR 223) and my girl locked up tighter than a virgin on prom night ! I cleaned and lubed her prior to the range so I'm not sure WTF ? The range officer had to come over cause I couldn't even move the charging handle and I had a live round in the chamber - we were able to get it open with a soft mallet and the range officer said it may be gunk build up in the chamber so I took it home and cleaned every part (including the chamber) like i was getting ready for inspection - I haven't had a chance to take it back to the range but I hope to soon .... I didn't see any huge build up of carbon in the chamber so I'm not sure if this is fixed - anyone else have any issues like this ? I'm a gov contractor who TDY's to the middle east 6 months a year so I'm very farmiliar with the issues with fouling on the M4 but I thought that since this is piston operated, I wouldn't have to be so diligent (lazy is my middle name) with cleaning - any info from those more experienced would be appreciated.