New setup for the R10! I would like your input!

[Nico5999]

GTA,

  My .20 cal Beeman R10 is quickly becoming one of my favorite rifles to shoot.  Today at the range I was printing 1/2" groups at 40 yards with JSB 13.73gr pellets (I could probably make these smaller with more practice).  Ultimately, I would like to shoot this gun in Open Piston Class Field Target.

  With that being said, I would like to upgrade my current rifle setup.  I currently have a Hawke Sport HD 4-12x50AO with a UTG one piece mount.  This is a pretty good setup...except that I want to shoot Open piston and the 12x isn't very conducive to accurate range finding.  With that being said, I would like recommendations on a scope that is (springer rated) with a MINIMUM maximum magnification of 20x.  Front AO is a preference but SF is acceptable (if a wheel is available).  Any type of reticle will work but target turrets are almost a must, as well as accurate and reliable clicks.  My maximum budget for a scope is $250 (mounts not included).

  In addition to upgrading my scope, the scope mounts will probably be upgraded as well.  Right now, I am thinking the BKL one piece mount would be superb.  However, the double strap are less expensive, but I am concerned these will not hold the scope securely onto the rifle.  Does anyone use these on their springer?  Do they slip?

Thanks,
Nico

[ptpalpha]

I use the BKL double-straps on my R11 and they haven't slipped yet.
As to the scope, I don't know if what you're asking for is possible within your $250 budget, with the possible exception of one of the older Philippine-model Simmons 44 Mag 6.5-20.  Front AO, target turrets, mil-dot reticle.  I don't know how "accurate and reliable" the clicks are, but considering the fact that it's an inexpensive scope (usually around $130-150 when you can find one, used) I have my doubts.
Other than that, you have the SWFA SS 20X (fixed) for $300, the Clearidge Ultra XP 6-20x40 for $370, the MTC Optisan Viper 6-24x56 for $420, etc. 
I can't think of any others that come close to meeting your criteria.  If you're interested in the fixed 20x SWFA, there are a couple demo models available right now for $260 + shipping on their samplelist page.