New saw works the best.
Hittin' metal in trees just seems to be part of the job. Sometimes you have a good idea it's gonna happen (old treehouse tree, fenceline) and you can just factor a new chain or two into the price of the job.
But my favorite is when I got my brand new 460 last year. I had dropped a 24" oak next to my house a couple weeks earlier and hadn't gotten around to cutting it up yet. Couldn't wait to break in the 460 on it. Came home from the dealer, gased it up and walked straight to the log. Didn't even have a spare chain yet. It cut in about 8" like a dream. And then the dreaded feeling you get when you hit metal and the shavings turned to dust. Man, was I pissed. Brand new saw. 30 seconds of run time. The chain wasn't just dull, it was missing teeth. When all was said and done and I had split out the offending piece I found a 2' long piece of 1-1/4 x 3/16 flatbar lagged to the tree about 6" from the side. Not that extraordinary if it hadn't been the first cut with my new saw. :censored: