[Thad House]

Originally Posted by Cory

Sprocket size is not your problem. We are using 16T AM aluminum sprockets in our drive this year.

What brand/source of chain are you using? We do not use masterlinks anymore, but we rarely if ever saw failures due to them (if we did it was usually because of shoddy installation by us) and definitely never saw pins failing in shear. You could have bad chain, but far more likely you have improper tension/alignment.

We are using this chain
http://www.andymark.com/product-p/am-0370.htm

Our chain from our center wheel to our outer wheels never broke once. These were tensioned using cams. Our centers were tensioned by moving the transmission up with washers to raise the distance. We use e-clips for alignment, so that doesn't change. The only thing i can think of and see is that the transmissions are bending under load, which could be changing the alignment and tension.
Those AM were the same sprockets we used at the beginning, and i can get you a picture of one that is round and is missing teeth.