On Fri, 18 Aug 2017 22:44:02 GMT, Terrance D McCarty
m wrote:

I am building a stand for one of my rain barrels, (full capacity 50 gallons,
or ~ 420 lbs).
I am using 3/4 inch plywood, and plan on supporting it every 60 degrees of
circumference with 2 x 4's with 2 or 4 in the middle of the circle.
Think this will hold 420 lbs.of water, plus 25 lbs of barrel weight? (Total=
~455 lbs)
Thank you.

You must be over thinking this project. Is the ground surface not good
enough to hold a barrel of water?

What kind of barrel are you supporting?