I shoot that bait a lot , which one do you have? There are many options but some are just finicky. Cold molds will cause some no fill problems too. The rings are hard to fill just by design and this sound really funny but the color you shoot makes a difference. Dark bait don't fill as well as light or clear baits do. Denting for sure if from to hot a temp. I shoot mine at about 300 but that is with my equipment so it will vary a bit. Shoot the bait as slow as you can with a firm push at the end to fill the tail out. This will force most of the air out. Make sure your injector is smooth by oiling it with worm oil. Put the injector in plastic till the whole tip is submerged draw plastic and shoot. Make sure the injector is big enough for the mold and remember you cant use all the plastic in the injector because it cools to much so plan on using about 80% ,more if you heat the injector. Also remember if the mold and injector is heated it take longer to demold.