When I first read the FAQs on bbl fitting I thought it should have a gap, But was informed by quick on another thread that it doesn't it is better if it doesn't. My first bbl fit was a 22" 20ga after about 15 minutes work on the underlug it locked up tight with no gap. As long as the latches correctly it should be good. I also bought a Tracker II 12ga bbl off MSP RET and it locked right up on an SBI frame I got from bobg no gap on that one either.