Chronos has some good points above.
Consider that in disciplines like F-class, you want reliable turret tracking for both elevation and windage. I started with my Vortex Diamondback 3-9x40. While i could see the bull at 5-600, after a few months, the frequent dialing for wind and elevation showed the turret tracking limitations of this sort of scope for that application when it would not go back to the same zero for 100yd after shooting 500 & 600, etc.. I still use it for set and forget hunting rifle but stepped up quite a bit to get good, reliable tracking. The Vortex DB is around $250-350, depending on mag and options, yet the other Vortex sitting on a clubs rifle is a PST and has held zero and been dependable for tracking for 2 years and they start at about $800 and go up to around $1100. They also do a very similar scope called the HST, which comes in at around the $700 mark.
In all honesty, this is the base budget price that i would start looking at scopes for this application. I don't have much money, so i would go cheaper if i could.
Can anyone name a scope under $500 (or even $700) that can reliably deal with regular adjustments to elevation and windage from shot to shot and return to a reliable zero at the end of the shoot?
There are a couple of Weavers and Clearidge scopes that would do the job well, but again, think they are around the $700 mark.
(all prices in US$ so add about %38 for exchange currently)
http://theopticzone.com/product/weaver- ... te-800363/http://theopticzone.com/product/weaver- ... te-849976/http://theopticzone.com/product-categor ... flescopes/http://theopticzone.com/product-categor ... flescopes/ (cheapest on this list)
http://theopticzone.com/product/sightro ... tte-63040/http://theopticzone.com/product/sightro ... tte-26006/ (what i ended up buying)
http://theopticzone.com/product/vortex- ... e-vhs4308/http://theopticzone.com/product/vortex- ... pst416s1a/http://theopticzone.com/product/nikon-m ... atte-6774/ (varying reviews on tracking when dialling regularly)
Anyway... good luck: but just remember, it's cheaper to buy a $800 scope than it is to buy a $400 scope and then a $600 scope and then a $1000 scope.