How to measure barrel length of S&W 29

[Redie Fredie]

I know this sounds silly, but just would like to confirm how (from where to where) to measure the barrel of a S&W 29-3?
The one I looked at Measures to be about 5 7/8 from muzzle to back edge of forcing cone. (guessing 6")
I am further confused by the "blue book" saying 29's were ...., 5", then 6.5",...
another fella's post states he has a 6" also, so the blue book must be hooie
 
Thanks for listening to me babble
Thanks even more if'n you can help.

[Graybeard]

Originally S&W used 6.5" barrels later changed to 6" but have offered 5" as well I believe. Yes that is where you measure and the lengths are nominal and not exact but usually pretty darn close.

[Redie Fredie]

Thanks for the Great Info Graybeard