Higher magnification useless! - Burris XTR II 8-40x 50mm Rifle Scope 34mm Tube Second Focal Plane SFP

I've always like Burris scopes and I have other brands, a Leupold VX6 and 2 Nightforce scopes(NXS 5.5-22x56 and 12-42x56 Benchrest model). I needed a high power scope for a 223 for prairie dog hunting and thought this would work great. It is clear and nice up to about 20-25 power and after that turns blurry and forget about 40 power! I tried readjusting the ocular and refocusing but it just isn't clear. I got this on clearance and should have known that if the price is too good to be true then it is! Thought about sending it back to Burris but I may just sell it and be done!