Are you using this tutorial?
http://www.thogamecalls.com/PDF%20Tutorials/TurningCrowCallsLattaMethod.pdfThe end of the guts should fit inside the live center on your tail stock. If they don't, and hold things together, no big deal. The end of the guts should just fit in the bore, so you can tape them to hold the guts together at that point.
Also, make sure you are not really cranking down on your chuck. You are just going to take light cuts to take the taper out so you don't need to really hog it down. Turn on about the third belt of you lathe for a smooth finish on the plastic.
The last trick you can use, is to take a piece of cardboard and cut it so it fits in the guts mouth part to help keep them from closing down.
I've run into this before as well, and these are the things I did to help cure the situation. They might work for you too. I think the key is to not crank down on your chuck too much.
The last thing you can try if you have a collet chuck is to mount the guts in the collet chuck in reverse of what the tutorial shows. This works too. The end will just go in enough to allow you to turn it. The tail stock live center will hold it together for you.
Much as I like this method of turning crow guts, I admit it can be a pain in the but to do. Please let me know if I can help you any more. I think we can get it so you can at least turn some of them without too many problems.
Finally, if you mess up any of the guts you got from me doing this, let me know and I will replace them free of charge for you.
Al @ THO