For sticks, you do need a 5# stuffer... about the bending... too much pressure was needed to get the meat through the tube.. BUT you already knew that.....
I use the 5# grizzly... plastic gears... I grease the piston and the meat canister really good... I lube the screws, shafts and bushings also.... for the metal to metal parts, I use the lube pictured below... It is a modified edible mineral oil... the same stuff you can take for constipation.... If it will lube you up, think of how good it will work on the stuffer allowing meat to flow easily... (I'm trying not to picture that.. It would be a picture that is difficult to UN-SEE)
What I did to reduce the friction from the tube was make my own tube that has a really thin wall.... I flared the end of the tube so it would stick inside one of the plastic tubes that comes with the stuffer...
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That tube is 1/2" OD because my flaring tool works on 1/2" OD tube... otherwise I couldn't flare the tube to stick inside the OEM tube...
The casing you see on the brass tube is 21MM but smaller casings will work... The extremely thin wall tube allows for a larger I. D. which reduces friction a lot...
It is important to really grease all the friction points very well... I like Crisco for the piston O-Ring and walls of the meat cylinder... It is really slick and the movement is friction free when you crank on it....
When I bought the stuffer I was well aware of the problems folks have had with plastic gears... Taking the extra precautions of lubing the stuffer has given me years of service....
Also, you can't allow the meat to sit and set up... It will get sticky and thicken like old gravy.... Season the meat, grind and stuff immediately... If you use a meat mixer to mix the ground meat... mix immediately after grinding and stuff immediately..... Then you can let the cased meat sit in the refrigerator for an extended time....
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The tube is available from McMaster-Carr... or some Ace Hardware stores have it... The tubing is mandrel drawn and extremely hard... It needs to be annealed when flared or solder a flared nut to it, or solder a washer to it to fit the stuffing canister... that will have to be made..
http://www.mcmaster.com/#8950k631/=10oyp9g
http://www.mcmaster.com/#8950k692/=10oypac
The flared nut below could be soldered on the end of the tube for a transition piece that allows meat to flow and holds the tube inside the OEM stuffer tube..
http://www.mcmaster.com/mv1452544250/#50635k555/=10oysc7
I flared the end of the tube and slipped a brass washer on it to help hold it inside the plastic stuffing tube... It ain't pretty but it works.... the tube on the left is copper pipe... it's wall thickness is MUCH thicker and causes more friction plus it is 5/8" OD.. It will barely hold 21MM casings... only about 36" at one time....