punky logs

[gtr]

Had a heck of a day sawing today. I cut into a total of 5 nice 20 to 26 inch fir logs and well over 50% of the lumber was punky.
From the outside the logs looked like any other is there someway of telling or at least suspecting that the a log could be punky.
Any info would be appreciated, cause it sure is frustrating to waste time cutting up a log that should go to firewood.

Thanks
GTR

[Tom]

Usually you can see that it is rotten.  I kick them sometimes and run my pocketknife into them sometimes and, sometimes, I just have to throw them off of the mill when I find out for sure. 

[sprucebunny]

I think that whacking them with a hammer or something , you should hear a difference in the sound.

[pineywoods]

The only sure way I have found is to put a sawblade to it. I cut a lot of lightening killed and bug killed pine. There's no telling how many trees I have cut, hauled to the mill, and then put them in the burn pile cause the lumber was punky. Sometimes even when the outside is bad, the heart may still make some fine lumber.