I use a 6.5-20 Weaver Grtand Slam for anything over 300 yards and it has been a fine scope, but if sticking to 600 yards I would probably be happy with some as low as 14x on the upper end, adjustable objective is a must though. You won't need a 20mm rail for 600 yard shooting, and although the 175 SMK is a good bullet I would probably try the 155 Lapua Scenar and see if the gun likes it.
For inexpensive scopes the Mueller APV Tactical 4.5-14 AO with 30mm tube is about $150 at Midway USA, Nikon Buckmaster 4.5-14 is around $300, Burris FFII 4.5-14 AO with Ballistic plex reticle is around $300 (I have one on my .300 Winnie and it is a good scope)is also around $300, Weaver Grand Slam 4.5-14 AO is about $350-360 and would be my pick of the bunch.
Going up to 16x you have the Millet TRS Tactical which gets good reviews but I have not tried one at $330, and the Bushnell 3200 and Burris FFII would also be in your price range.
At 20x the Weaver Grand Slam 6-20 AO with Varminter, Ballistic Plex or Target Dot (this is the one I use) is about $370 and I really like the glass in this scope for the money. The Leupold VXII's just make it in your range at $500, Bushnell 3200 7-21 AO Mil Dot also makes it under your limit, as does the Burris FFII 6.5-20 with a choice of reticles.
If I was going to buy another target scope today I would go with the Grand Slam 6-20, I love mine and the glass seems a bit better than the Leupies, Burris , Nikons and Bushnells I also have.
. If I told you that I used a Flecker scope at one time you’d wonder what in hell he is mumbling about. You might recognize Unertl I had couple of those also.
