It's really just a starter scope for now so I can do some shooting.
Most of the good quality long range scope don't go past 25 power magnification. I had this scope and at 24 power it's already not as clear as 6 power. http://www.opticsplanet.com/vortex-viper-pst-6-24x50-ffp-riflescope.html
And that is on a $900 scope. I can only imagine how bad the blur is on a low quality glass scope.
And there is absolutely no need for a 40 power scope. Especially not at 600 yards.
Buy a good quality scope like vortex or leupold in a 4-12 and you will have no problem making hits at 600 yards.