At Chuck Hawks website, he has an article on Maximum Otimal Ranges for various rifle calibers. The web address is:
http://www.chuckhawks.com/game_range_caliber.htm
I hope the link works for you.

In the article, there is a chart that gives the maximum ranges at which various types of game could be taken with quite a number of calibers, including the 6.5X55 for which the maximum range for taking animals of 200 lbs or less is given as 400+ yards.

I do believe that if one wishes to try shots at game animals at such ranges, one should spend some time on a rifle range finding out exactly what his rifle does at such distances. Personally, I have taken game (a large bull elk) out to slightly over 500 yards with my .300 Weatherby. I also shoot fairly frequently in the local groundhog shoots where we shoot five rounds each at 200 Meters, 300 Meters and 500 Meters. 500 Meters is about 545 yards. I know exactly where my bullet will strike at 500 Meters, and carry a rangefinder and a table on a card in my wallet that tells me how much drop to allow for at 100 yard increments.