I have never used the swell-neck rivets. They're a waste of time, and they will have zero effect on the function of your AK. You can trust me on this. I've built over 30 of them, and several of them have more than 5,000 rounds through them without any rivet failures. On full-auto fire or when launching grenades the extra friction might make a difference, but under ordinary single-fire conditions the swell-necks are entirely unnecessary. Hell, I even bump-fire mine all the time. So far zero failures.