Why aren't my home made hot dogs snappy?

I made hot dogs (homemade) the other day. They were beef, and I used natural sheep casings. I smoked them until fully cooked (about 160, but one batch got up to 170 or 180), and then have been reheating them on the grill. They are not snappy at all and the texture is more like hebrew national (not bad, but not what I was hoping for). What affects the snappy-ness of hot dogs? Would overstuffing them do this? Or overcooking? Also, a side question, after twisting sausages into links, do you just cut them with scissors to separate? How do you prevent the ends from opening up?