In an earlier post, Weaver Super Slam 4-20x50 was mentioned. This is a very nice scope....own 2 of them and one 3-15x42 super slam.
Club I'm a member has a 600 yd range. Seldom shoot there, but when I have, used a rifle with a 4-20x50 Super Slam on it since they are on my most accurate rifles. Scope has enough vertical elevation to adjust it for trajectory at 600 yds. Optics in a Super Slam are quite good. Very clear and bright at all powers and very comparable to higher priced brands. You should be very pleased with any of the scopes adjustments too.
Might want to check the super slam prices at www.natchezss.com
After checking Natchez prices, compare them to SWFA, Amazon, Optics Planet, Midway and etc. You should find Natchez the lowest priced.
Depending on the reticle Natchez prices are from $580 to $630 (plus about $15 shipping) Weaver presently has a $100 rebate on the 4-20x50, but not sure all three of the versions of it qualify. Recently bought the dual-x model and sent in my rebate info to Weaver.