How is the baler going to handle chopped up straw in a large windrow???? Your NH 273 is not a very large capacity baler. The fine chopped straw feeds in tough. So you add in the big windrow and with the small capacity baler an you will have trouble unless your tractor has a real slow low gear.
The feeder teeth you see will usually work even with out the little springs on them. The trouble is the shot cut straw. The fingers pull through the fine straw as there is nothing much to hold the straw together as the fingers pass through it.
Also the fingers are supposed to ride up over the straw/hay on the back stroke. Then on the forward stroke they swing down and spear the material and move it into the bale chamber. I bet that if you try the baler in hay it will work fine.
Straw is harder to bale. Chopped up straw is VERY hard to bale. Sometimes next to impossible to bale.
I had a NH 273 years ago and the little springs where broken half the time as they did not last very long. It did not make much difference in how it baled.
I think your problem is the material more so than the baler.