My bar on my Echo 58V is a .043 gauge and it was bad about throwing the chain. I went to Tractor Supply and bought a .050 gauge chain, same length, same number of drive links, same pitch, but .050 gauge.
It was a snug fit in the bar groove but it went on. The bar smoked for a few seconds when I started running it, but after a few seconds of running time the drive links and the bar wore until they fit each other. I'm on my third .050 gauge chain on that .043 bar now and the groove in the bar has opened up enough that the .050 chain fits. It's not prone to throwing chains any longer.
