thanks. As it turned out I did use a pork butt, cost only $1.48/# on sale and pork fat appears to be running about 50 cents more. Pure fat is a lot harder to come by, guessing because there is just less of it – supply and demand. One recipe I was using called out pork fat and I directly substituted the ground pork butt and it tasted fine even at a 25% ratio. The other sausage experimental batch I made with 50% and it is even better. So, 50/50 is the future now. thanks for your input folks!

Jonathon It looks to me you may have missed a small point in the original post. He said he was using 16mm casings but a 3/8" stuffer tube. 3/8" is VERY small-- only 9.5 mm! He is trying to punch it through a pinhole darn near.